no prob. BTW it mihgt be good to have a "general discussion" type forum in this group. not everyone is maing stuff for dota and tf2 only. (I wasn't sure if this was the best place to post a link to this guide but it seemed to be the closest one of the choices).

You probably need to change your world material so you have some global ambient lighting for an AO map. Some types of baking are based on lighting, whereas some (like normal maps) don't take it into account.

With cycles you need to make sure you have a texture node (at least one) in the material asigned to the object. For bake to work, that node must be the currently selected node in that material. This means you can have multiple texture nodes and to control which is usd for output, just make sure it's the active selection. Also make sure you already created the image to bake to (so you can control the size etc) and make sure that image is in the node.

What were you trying to bake exactly (what type of bake) and what didn't work?

Also, it may help to go into edit mode on the object and do a select all (A) on all the faces. Baking may only operate on selected faces.

Here's a tutorial that is actualy for the game Blade Symphony but may help people using blender for other source engine games:

http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=291006800

I'd use Cycles for this. I've run into too many bugs trying to bake with internal.