Terrans are the easiest race to get used to, nevertheless, to play well with them you need much help.
Zerg are hard to play, but if you master them you just might be a new Battle.Net champion of Starcraft.
Protoss can be played and mastered with relative ease. However, their units are pretty costly.
This is a must read for all of you. The essence of the game is: management and scouting.
Here are some of the best advices how to adjust your race's tactics in 1v1 games.
Here are some received tactics from fans that have been tested in real conditions.