Keystrokes:

In the readme file you can find help on keystrokes. Also, under F1 there is a keystroke help file to read. Read these and learn them well.

Learn the hotkeys for building men and structures. Always use hotkey for special abilities. Nothing is worse dying because you couldn't cast Psi Storm, Lockdown, or Plague in time.

Use the "ctrl + #" hotkeys to group your units in an organized manner and keep important unit producing buildings quickly accessible. Just don't go overboard with organization because time is so precious.

Use the "A" attack hotkey to move units through areas that aren't visible. This way they attack anything that's a threat along the way and then continue their journey after fighting. Use the "M" command to make your units move away from a losing battle without ever turning back to fight when you don't want them to. The "S" stop hotkey is great for getting your men to disregard your last order such as attacking a certain building when you want them to auto-attack other enemy units near them.

The "P" patrol hotkey also has it's uses. Use it when amongst buildings or a mix of buildings and men.

Again, a better key to use for attacking in most areas is the "A" attack hotkey. Select your group and hit "a" then aim past the target units. Your men will walk towards them and start attacking as soon as in range. Make sure you specifically tell guys to attack men if they are going after buildings instead.

The right click is used for many things including to move units. Use it often, but beware of it's weaknesses. The specific hotkeys are better to use in many situations.

Sometimes it is much better to have grouped ranged attackers walk (right click or "M" for a definite move without attack) nearer the enemy and then have them attack using the "A" hotkey. This way they'll all get to attack instead of only the ones in the front and is much more efficient.

To attack a building without being attacked from behind, "M" move your guys to the building. Only right click your units on the building if you are watching your units, or they'll be attacked from behind and die.

Attack types and Unit Size:

In the readme there is a section on the types of attacks and the sizes of units. This greatly affects which units are good against which. For instance, Vultures do great damage against Zealots but hardly any damage to Dragoon's HP's. Learn all of these distinctions well!

Save your fighting men that are being hurt. Walk the ones in the front lines who are getting attacked to the back; if they will make it, you will still win the fight. Sometimes depending on the situation it is more efficient to let them fight it out.

Right click units on other friendly units to make them follow. This keeps them from ever attacking and is especially useful when you don't want certain units to attack and alert the enemy of your presence, or to save Protoss Reaver's scarabs from attacking the wrong targets.

Use hit and run tactics for fast ranged units against melee units if it kills them better and you have time to do this.

Use hit and run tactics with shield batteries for the Protoss.

Burrow Zerg units when they are at risk of dying and there is no anti-burrow devices around. Remember that if they are being hit frequently they cannot burrow.

If an enemy is after one specific unit, have him run in circles around friendly units or towards friendly units.

Spread units out to avoid area effect specials. Keep your men moving and there will be less of a chance they will get hit with the special. You can also place air units above their own units so their units will get hit by the special too. Send one or two units to take out the "casters."

Get all your fighters together when you mount an attack (unless you need a few on defense). Use the shift key to keep selecting units, then move them all to the same location. The best way to do this is to right click them all on the selected unit that is closest to the area you want to go to. That way they will break formation and come together. Beware of ambushes while doing this.

Use a few men as a distraction and sacrifice to allow you to cast area effect specials more accurately. Simply have the decoys fight the enemy and then you have the best casting opportunities.