What’s your Starcraft 2 advice or tip?

Ideally one should never have more than ~300-500 minerals sitting around doing nothing unless you're saving for an expansion. If you can't get rid of excess minerals, use all of them to build more unit production facilities to prevent the problem from occuring again later in the game.

Keep building workers constantly throughout the game. Ideally, one should be building at almost all times. This will give you more workers than you need, but you can always transfer those extra workers to a new expansion.

The cost of a worker or cheap combat unit is insignificant compared to intelligence on what your enemies are up to. Scout early and often!

Spend your resources. If you are gathering more than you can spend build more unit-producing structures or purchase upgrades. Losing a game with a high number of unspent resources is a sign that you need to be more aggressive with your spending.

Use the attack-move command (rather than the plain-old move command) to make sure that your units will engage any enemies they encounter on their trip. Select your units and press 'A' then left-click (alternatively, you can use shift + right click)

As Zerg, you may want to consider building more than one Queen, even before you get your first expansion, for two reasons. One, for extra air defense versus early Mutalisk/Banshee/Void Ray attacks (as there are no other Zerg units that can attack air until you upgrade to a Lair), and two, so you can build LOTS of Creep Tumors to greatly increase the mobility of your army and to increase your constant vision on the map.

As Terran, versus Protoss and Zerg, you should consider blocking off your main base's choke point with your first Barracks and some Supply Depots, so Zealots and Zerglings can't make it into your base. Be wary against Zerg however, as this is easily countered by Banelings.

Learn to love unit groups. Select units and hit ctrl+# (like ctrl+5). Now, when you hit 5, you'll automatically reselect that group of units. Hitting 5 twice will center your camera on the units. Make sure to assign your bases a group # so that you can quickly and easily bring it back into view.

Minimum 22 workers. You need at least 2 workers for every mineral patch (most maps have 8 in your main), and 3 per vespane geyser. Economy is a huge part of the game.

A good, simple Protoss tip (maybe other races too) is to set your Nexus waypoint (hotkey: Y) to the minerals. You don't have to worry about making sure you assign them to a task when they pop out, as they'll go straight to collecting minerals. From there, just peel them off the minerals to do different tasks.

Make sure to queue commands by holding shift while clicking a mouse or hotkey. For example, if you assign a worker to build something, shift + right click the mineral field so that he goes back to mining after being done building.

Use the terrain to your advantage. High ground grants you a great advantage (which is also why its important to spend the 1 unit to capture/hold Xel'Naga watchtowers). Also, Reapers and a few other units can move up and down cliffs, allowing you to quickly cut through the map and get behind enemy lines.

Zerg players should research burrow so their Roaches can heal themselves while burrowed. The hotkey for burrowing is 'W'. Whenever a roach is being focused fired, burrow it when it reaches ~25% health and unburrow it once its healed up.