Ambushes what types of troops do you use

[Alexios]

Ghazis are good for wood ambushes in defensive battles. You have to position your main force next to a wood and hide the Ghazis there. If you keep your general at that side and leave your flank seemingly exposed (apart from the forest) the AI may start maneouvering up that flank, if you're lucky... straight into the waiting axes of the Ghazis.

The way I usually like to use the ambush strategy with infantry is on the edges of my spearwall. Whether I'm attacking or defending, if I have many spear units with ranged units (which I usually do), I will almost always line up my spearwall so that one flank is near the edge of the woods. I then hide an infantry unit or two within the woods, so that if the enemy attempts to flank my spearwall with cavs, which oftentimes they will try to do, I will ambush them from their side or rear. The results can be most devasting... for the enemy that is.

Lately, I usually play as English, so I find the clansmen built in Scotland to be a highly-effective unit for such ambushes when used in early or mid. They are also very inexpensive to build and support.