Which race will you play for your first multi-player match? Forgive me if I am wrong but though this thing runs for a few days in B.net I haven't seen it here.
For my part I'll get the hang of all 3 races in Skirmish/Campaign first. Get to know the tech tree before getting my butt handed over in Multiplayer.
Firstly I'll play the campaign (ofc!), then read on teh interwebz on what race is op and needs balance and play that before they patch the game and fixes it. srsly tough, I'll go for random
First I'll go random because it's the best way to learn all the races (and it's fun to anticipate which race you're going to play). Then once I have enough experience playing all three races I switch to Terrans and try and master it.