Which bnet server do you use? You can find me at US West in channel
clan starbruisers
I am not affiliated with that clan, but I hang out in there. My buddies and I play Broodwar almost every day and we often engage in watching replays of professional Broodwar players.
Becoming a pro in the USA is difficult since there is limited company sponsorship and since the game isn't taken nearly as seriously as in Korea. In Korea there are 3 television channels dedicated to airing Starcraft tournaments and Starcraft affiliated programs. There are huge company sponsorships and lots of potential money involved (but you must be extremely good). The top Starcraft player in the world pulls in $180,000 a year (U.S. funds). The best USA players are flown to Korea to compete in world tournaments.
Warcraft 3 has been shunned by most of the professional gaming community since the depth of in game strategies is far more limited than Starcraft. It is a much slower game and lacks the same sort of diversity that Starcraft has. Also, War3 still has many balance changes yet to be implemented, not to mention that the expansion for the game will be coming out shortly and is still in beta. Starcraft has been balanced to a very fine point and is very stable, thus it is a game where you can get comfortable in and stay comfortable.
Here is a good resource to start your training:
Professional Map Index
This is a site by a good friend of mine which includes current and past professional maps that can be viewed and downloaded. Learn these maps well if you have any inclination of becoming a pro.
In the most general pointers I can give you (I'm not a Protoss player, I'm Terran only and would love to challenge you sometime) are these:
Keep producing Probes, you can always transfer them to new expansions later for economic boosts
Maintain good recon, know what your enemy is up to, so you can expansion deny and be ready to counter when necessary (and be ready for any enemy shift in tech)
Use game hotkeys and control groups in order to have more precision control and speed
With Protoss it is very important to macro well (keep up production), never have an excess of resources since that means you're not producing fast enough, in order to keep up, you must warp in more production facilities
I am just barely skimming the top, if you have any further questions, do not be hesitant to ask. Good luck!