When units or sprites are selected, use the arrow keys to move them by one pixel at a time.
Use the 8, 4, 6, and 2 keys on the number pad (remember num lock!) to scroll the map.
Press the number keys 1-9 to set the current player.  Press 'P' to set the focus to the player number box.
To stack a unit such as a mineral block, place it and select it.  Change its properties to the desired amount.  With it still selected, right-click and select "Stack."
Locations, sprites, and units can all be aligned to the grid.  There is a grid snap button on the toolbar, and you can also press F4 to toggle it on or off.
Viewing the grid can be toggled by a button on the toolbar or pressing Ctrl-G.
The grid settings window allows you to change the grid size, offset, and color.  Access it by pressing Ctrl-Shift-G or Edit -> Grid Settings.
