Hint :
Zerg secret level:
Successfully complete level 9, "The Reckoning", in under twenty minutes to unlock a secret level. Unfortunately it does not permanently appear on the level list. Save at the start of the secret level in order to easily play it again.
Hint: Interfering with CPU mineral production:
Note: This trick works best when playing as the Protoss and SCVs and Drones are used. Build a Pylon with Cannons near an enemy base, but not in it or near its mineral production. Get a Probe and attack their base, unless it is a suicide mission. Immediately after that, run to your cannons and watch the enemy workers die. If you do this rapidly enough, eventually they will quit making workers and just sit there.

Hint: Destroying Siege Tanks:
Get a large group of Dragoons (nine to twelve), and they can easily overpower Siege Tanks.

Get a unit that has to get close to another unit to attack, such as a Zergling. They can take out a Siege Tank because tanks can only attack units that are far away.

Hint: Extra Broodlings:
When playing as the Zerg, enable the show me the money code, or have a lot of Queens. You can keep using spawn Broodlings on other Broodlings. In a short time you can have 50 Broodlings, and attack. Use this trick when your opponent only has an infantry.

Hint: Quick start for Protoss:
First, get the first four Probes to start gathering. After doing this, build five more Probes and put all of them to work except for the fifth. This is the one you will use to start your building. Once all Probes are built, build two Pylons, preferably close together. After completion of the Pylons build two Gateways and proceed to start pumping out Zealots. After you have maxed out at 33, build more Pylons, By now you should have a big enough force to hold off the first round of attacks, However, remember to keep building Zealots to replenish destroyed ones.

Hint: Easy attack on enemy bases as Protoss:
Play as the Protoss and mine enough minerals so that you can build multiple (three to five) Arbitors and place them around key locations, enemy bases, or places that you would normally need a shuttle to get to. When you build units, you can use the Arbitors' "recall" ability to get your units where you need them much faster than it would take to use shuttles or move on foot.

Hint: Fast Zerglings:
Have your four starting Drones start harvesting. Build only one more Drone. When it hatches, have it harvest. Wait until you get 200 minerals, then build a Spawning Pool. When you get 50 minerals, make a Drone, then another. When you get 100 minerals, make an Overlord. You should have 6 Drones, about 150 minerals, and 2 Overlords when your Pool is done. This takes about two to three minutes and all comps will fall to you, even the hardest ones.

Hint: Defeat an enemy quickly with Terrans:
Bring in a SCV behind an enemy's base and build a Barracks. Start cranking out the units and attack. If you cannot get one, then build a Barracks and then fly it over behind the mineral field in a moving city tactic.

Hint: Saving money:
If you run out of Minerals, move the Command Center to a mineral field. Bring an SCV to the back of the mineral field. Build a Barracks, crank out the units and attack. Click on a Barracks then press M for marines and F for firebots. Click on an SCV. Click "Build" then press B for Bunker, S for Supply Depot, and T for Turrets.

Hint: Legacy of the Xel'Naga (Protoss Level 4 Brood War):
First, build everything possible to complete your base. Make sure you have a lot of Protoss Cannons surrounding your base to fend off Zerg being transported by Overlords. When you base runs out of minerals and gas, head northwest and start a new one there. Since the entire island is surrounded by Spore Colonies, you need Corsairs, Shuttles and Dark Templars. Fill at least two shuttles with Dark Templars and send the Corsairs to do their "special disruption" on two or three Spore Colonies. Next, unload the Templars on the island. Since they are invisible, slowly take out the Spore Colonies. Usually Queens will splatter green liquid on them, making them go slower and become visible -- be careful of Hydralisks and Zerglings attacking them. When you destroy all the Spores, send over a Probe and build two Pylons, five Photon Cannons and a Gateway on the island in an empty location. The Photon Cannons will kill the Hydralisks and Overlords that approach. Then, get the Corsairs to use disruption on the Sunken Colonies and the Hive. Next, send in as many Dark Templars and Dragoons as you can to take out the Sunken Colonies, then the Hive. After you destroy one half of the island, the rest will be easy.

Hint: battle.net abbreviations:
The following are abbreviations used on battle.net, and what they mean:

gg: Good game
gl: Good luck
rm: Re-make (remake the map)
bc: Battlecrusier
goons: Dragoons
lings: Zerglings