When playing each race when should you send your scout out when playing each race to gain a better knowledge of the opponents plan ?
Depends on your own race. As terran, send about your 9th scv to scout, since nothing will get to you before your wall is up. Same for toss, I think. As zerg, you might want to know very soon if you will get proxied/2 gate rushed or 6-pooled, I usually scout with 7th or 8th drone. Mainly bc this decides if I fast expand or not. Then, after some minutes, it's good to scout again to see what the opponent is doing after he feels secure to do so unobserved. This will be the tricky part, since every race will make it as hard as possible for you
I'd agree with what doman said. You essentially need to scout late enough so that it matter but early enough so that the base isn't walled off. That's usually around your 9th or 10th unit.
