Settings
The Settings window is where you tell Moom how you'd like it to behave—in general, and for mouse and keyboard usage. In addition, the Custom icon can be used to create Custom Controls, which can greatly extend Moom's powers.
General Settings
The General tab of Moom's preferences lets you control some aspects of Moom's general behavior.
The Grid/keyboard control highlight can be used to make it more obvious as to which window will get the resizing action you're about to apply. The window is highlighted by dimming the background; as you move this slider, you'll see a live preview of the effect, as shown on Moom's settings window. If you set this slider to Off, Moom won't dim background windows at all. (This will also disable the grid preview feature; see the Mouse section of Usage for more on the grid preview feature.) Note that you'll only see this highlighting effect when resizing via the grid, or when using the keyboard.
The Separate windows by nn px option (which is not enabled by default) controls the amount of spacing between windows when using the grid or Move & Zoom actions. When disabled, Moom will place windows directly along screen edges, and run them right up against other windows. With this setting enabled, windows will be spaced by the number of pixels you designate, including moving windows away from screen edges if you check the Apply to screen edges box.
Certain Mac applications—TextMate, BBedit, and TextWrangler among others—use drawers to display additional information beside their main windows. Enable the Treat drawers as part of their parent windows, and Moom will treat the drawer as if it's part of the main window. This should lead to more accurate positioning via Moom.
Launch automatically at login and Show settings on launch are straightforward, and do what you'd expect. If you want Moom running all the time, and want it to launch silently, then reverse the default settings—check the first box and uncheck the second.
The Run as pop-up menu lets you specify how Moom will operate. When run as a 
application, Moom will have a Dock icon when running, and it can be selected like any other application.
If run as a 
application, you'll see the Moom icon in your menu bar; click the icon to reveal a menu that lets you reach the settings screen, quit Moom, and more.
If run as a 
application, Moom will be invisible—no Dock icon, no menu bar icon.
To access Moom's settings when used in faceless mode, double-click the Moom icon in Finder. Launching the app when it's already running causes the settings window to appear. To quit Moom when in faceless mode, first launch it again, then click the Quit Moom button at the bottom of the General tab of the Settings window.
Mouse Settings
This tab of Moom's settings controls how Moom interacts with your mouse.
If you'd like to control Moom only via keyboard shortcuts, remove the checkmark from the Pop-up mouse controls when hovering over a Zoom button option.
If this option is grayed out, that's because you haven't set up any other way (general keyboard shortcut or custom control) of controlling Moom. Once you've done that, you can disable the pop-up mouse controls.
The slider controls the amount of time you need to hover over a green button before the pop-up controls appear. The default is 0.1 seconds, the minimum delay is zero, and the maximum delay is one second.
Check the Enable Move & Zoom grid with option to have Moom display a small grid-based representation of your screen below its usual mouse interface. (Read more about the grid in the Usage section of help.)
You can use this grid to size and move windows to somewhat arbitrary sizes and locations by drag-selecting cells on the grid. You can also change the size of the displayed grid by changing the two numbers here (6 and 4 by default).
Moom lets you create Custom Controls for any number of move and/or zoom actions. If you check the Enable access to custom controls box, you can access these (typically keyboard-only) custom controls from Moom's mouse interface.
With this option enabled, you'll see a small 'person' icon in the Moom mouse interface. Click that icon, and Moom will display a drop-down menu containing your defined custom controls (as seen in the screenshot at right).
If you also check Show on hover, then you won't have to click the person icon; merely hovering over it for a split second will reveal the drop-down menu.
The Bring moomed windows to the front automatically option controls what happens if you use Moom on a background window. By default, Moom will bring any window that you've modified via Moom's mouse mode to the foreground. Uncheck this box to leave background moomed windows in the background.
If you hold down the Command key while invoking Moom on a background window, Moom will do the opposite of what's set here. If Moom's set to bring background windows to the foreground, holding Command and invoking Moom on a background window will leave that window in the background (but it will be moved and zoomed based on your chosen action).
Keyboard Settings
When first launched, the Keyboard tab of Moom's settings screen is quite limited:
To use Moom via the keyboard, you need to set a trigger key that will activate the Moom keyboard bezel. Once you've assigned a hot key, the panel's appearance will change, as seen below (settings have been modified from their default values):
Here's what each of those expanded options does.
Click the Show cheat sheet box to have Moom display a list of your defined keyboard shortcuts, just below the onscreen keyboard bezel. With the cheat sheet active, the keyboard bezel will remain onscreen longer, too, so you have time to read the cheat sheet.
If you create custom controls that only work when the keyboard bezel is onscreen (see the hot key section of Custom Controls), those commands will also be shown on the cheat sheet.
Here's an example of a cheat sheet, showing a mix of onscreen-only shortcuts (the single keys) and the defined Moom actions (those with the arrow keys in their description):
The Repeat to show grid option enables grid-based resizing via the keyboard. Once enabled, if you press the keyboard control trigger keys twice in succession, the Moom keyboard controller will be replaced by an image of the resize grid:
With the grid onscreen (it's sized using the settings in the Mouse section of Moom's settings), use the arrow keys to select the starting cell for your grid, then press and hold Shift, and use the arrow keys to stretch out the desired size and location for the window.
After drawing out your region on the grid, press Return and Moom will dismiss the keyboard grid panel and resize the active window.
Assigning actions to keys
The section below the trigger key assignment area is used to assign actions to various keys. The first four actions control what the directional arrow keys will do, either alone or when used with modifier keys:
Each of these four options can be set to one of six actions:
Move & Zoom to Half Screen: This mode mimics the mouse-activation usage of Moom. Using the defined shortcut, this action will move the frontmost window to the specified screen edge, and set its size to half the available space, either vertically or horizontally depending on the chosen edge. (Assigned to Command plus arrow keys in the default configuration.)
Move: This mode will move the frontmost window 50 pixels in the specified direction. Press the arrow keys repeatedly to move the window around the screen. You can move a window beyond the edge of a screen when using this mode.
Move — Confine to Display: This mode is identical to Move, except that Moom will not let you move any portion of the window beyond the edge of the display. (Assigned to the arrow keys in the default configuration.)
Hold the Shift key to move in one-pixel increments (instead of 50 pixel increments) when using either Move or Move - Confine to Display.
Move to other display: If you have more than one display on your Mac, this shortcut will move the selected window to that display, without resizing it. (The window will be reduced in size if that's the only way it will fit on the chosen display; it will never be scaled up, though.)
Grow: Allows you to increase the window's size using the arrow keys.
Shrink: Allows you to reduce the window's size using the arrow keys.
You probably don't need to assign both Grow and Shrink, as either mode can do either action. The only restriction is that the arrow keys' initial action will be to either increase or decrease the window size, depending on if you've assigned them to Grow or Shrink.
After the initial press of an arrow key (with modifier, if defined in that way), the window will grow/shrink, based on the assigned action. After that initial action, though, you can use the opposite arrow key to reverse the action if you press it without too much delay.
For example, with a Grow action linked to the arrow keys, pressing Right Arrow will grow the window, from the right edge. Pressing Left Arrow immediately after Right Arrow will shrink the window, again from the right edge. Keep pressing Left Arrow and Right Arrow (without too much delay), and the right side of the window will shrink and grow. If you then pause for a second and press Left Arrow, you'll see that the window grows from the left edge, and you can shrink it with Right Arrow (again, if you press it without too long of a delay).
Although complicated to explain, this dual functionality of the arrow keys makes it easy to shrink or grow a window with only one assigned arrow key command.
The next set of four options are used to set the behavior for three special Moom keys: Return, Tab, and Space.
These keys can each be set to perform one of four actions:
Move & Zoom to Full Screen: Zoom the frontmost window to full screen mode.
Center: Center the window in the screen. This center command uses the OS X standard "upper vertical" center, which places windows above the horizontal center of the screen.
Center—Actual Screen Center: Just like Center, except positions the window at the absolute screen center.
Revert to Original Dimensions: After moving a window using Moom, this option will return it to its previous location.
The final section of the Keyboard tab controls the actions that cause the Moom bezel to immediately vanish (after performing the specified action).
If you'd like the Moom keyboard bezel to remain onscreen until it times out, make sure none of these options are checked, as in the above screenshot. (By default, the 'Other actions' box is checked.) Alternatively, if you check any of the above items, then the Moom keyboard bezel will vanish as soon as it executes the specified action.