Usually you would notice the changeling when you try to move your army and you notice that got one unit not moving.
Usually if want to sneak a changeling in, you would have to sneak it at a spot they won't notice. Not easy though if they put up turrets around the base.
But later they move the army that time also they'll start to notice. Why that marine not moving one haha.
Oh yea. Can just set it to follow one of the troops.

A few things to be vary of for various races.
The hard part is still scouting the terran as they wall off.
Worst case would be to sacrifice 1 overlord hovering nearby just to see what structures is he going.
This is usually for cases that are not cheese since it was already covered above.

Terran:
3-4 barracks with tech labs.
Incoming marines and marauders on the first attack or only marauders.
Concussive shell and stimpak is probably on its way.

Barracks with a reactor and you managed to see a factory.
Watch out for hellions. Try to block your ramp with units and move your spine crawlers to it when creep reaches there.
Best is to just get speed for your lings to counter this.

He is going 1/1/1. 1 Barrack, 1 Factory and 1 Starport.
Mech build incoming. Mostly marauders, tanks and thors with vikings and medivac.
I seldom meet this as protoss though. Should usually happen against zerg players.

Zerg:
A roach warren after the pool and hatchery still not upgraded to lair.
Incoming roach with ling rush.

Lair almost immediately and there's no roaches.
It's either hydralisk or mutalisk. Watch out for which building comes out first. The hydralisk den or the spire.

Protoss:
2 Gates up before the cybernetics core.
Watch out for a zealot rush. Usually next you see is another 2 gates coming up.

2 gates and then a cybernetics core. He is going the normal zealot, sentry and stalkers.

1-2 stargates
Phoenix or void rays are coming.

robo facility with 2 gateways
Immortals and probably colossus is coming. Watch if he builds the robo bay.
Hard to scout this out though as it is already late game and there is probably a lot of stalkers to shoot down your scouting overlord.

Hope I got those right.
Please add or correct me if I'm wrong.






This post has been edited by tatyinw: Sep 8 2010, 01:46 PM

Hmm I'm actually not sure why.
Saw it in one replay where the caster said that as the terran was against zerg.

As he went straight to starports and only 1 rax, chances are low that he is going bio ball.
You'll probably either see 2 factories or 2 starports coming next according to what he scouted on you.

It is mech because it is all going to be mechanical units I think.
You may have to check with a terran pro.
I'm more of a protoss player.

Haha that's a really bad tactic to use against zerg especially when you can pool early and nothing he can do to stop your zerglings swarming him down.
He was really asking for it. It works best against protoss and nice also against terran. Even though terran can lift and land somewhere else, the protoss player already denied his economy for that amount of time to lift and land.

You can also just keep going lings and rushing into his base and destroy everything.
The ling rush part happened to me. Could not really contain him and I got overwhelmed later in the game as he kept harassing my expansion when we were both really low on resources. The ling part was actually at the beginning and at the end. He did go hydralisk in the middle but I think he gave up on it after meeting my phoenix army. If you want I can post the replay for you to see how he played with his speedlings. He was quite good at using them to harass non-stop.

This post has been edited by tatyinw: Sep 9 2010, 11:21 AM

Ah...
Think he probably should have gone 2 gate.
But then, if he go and proxy like that. His base would be totally open for attacks...
That's the worst risk to take against a zerg player as toss.