I'm Zerg (platinum, near diamond) and I want to know how to interpret my early game scouting against Protoss.
I imagine that I need to know the different timings of build orders, how many Assimilator/Gateway/Cybernetics Core/Robotics Facility are required. I know that there are plenty of different builds but I need to know the main ones.
Globally, how should I react if I see at 5-6 minutes no expand or 0/1/2 Assimilator(s) on expansion?
To start this off, there a billions of timings against each race that you need to learn and become aware of in SCII. Being at a "near diamond" level, you should be aware of the timings in the following list: Here on teamliquid
If there is no expand at 5-6 minutes, according to the current meta game, it means you're being cheesed or all-in'ed. Possibilities include 4-gate, 2-Gate(Zealot cheese), cannon rush(forge hidden in base), proxy gateway(zealot cheese), and there isn't much else the 'toss could be doing unless he simply doesn't know how to play. To check for the cheese send the overlord into his base to check.
The basic guidelines are, if you don't see gas at the opponents natural at around 6 minutes, you're going to see aggression soon. I can't possibly hope to go into detail on the types of aggression Protoss can do with different gas timings. This is something you should look into, teamliquid.net is a great resource for this type of stuff. If Protoss takes more gas, then typically it means less chance of immediate aggression. Equally important, if not more-so, are timings on his third base. If you notice the Protoss does not take a third, it means aggression is coming very soon.
Against late game aggression you should do the standard three bases, and react to what you believe is coming. I cannot post the answers to each of the different compositions and what you should make against them. The standard is to go 'ling, roach, into late game infestor/brood tech. Some Protoss builds are now countering this style and there are 'ling/muta styles as well against Protoss. I recommend checking out TL to find out the different builds they can do and what the counters are.
Well most of it comes from experience, but some usefull tings to look at:
The most obvious: search for what kind of production buildings your opponent is building/has builded (mech producing facilities or infantry?, working forge means upgrades, fer example with protoss fleat beacon means carriers or mothership
Gas (assimilator, refinery, extractor): no gas probably means cheesing or early agression, 2 gas is probably mech based.
A usefull tip to better-playing starcraft in general: if you are zerg you should take a little time to play as protoss and terran it is easier to win when you know your opponent ;)
