P- Show guide.
S- Stop unit's current action.
Escape/Space bar- To un-select units.
Tab- Reveal all armor bars.
0- Select Mother ship.
1-9- Load Unit Group.
Control 1-9- Save current unit selection.
Mouse click (Unit)- Select unit.
Shift Mouse click (Unit)- Add/Remove unit to/from group.
Select group of units with your mouse.
If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).