I am going to create the AI for a squad-based FPS game, but since it is the first time I am creating AI for such game, I would like to hear some comments on how to get started.

Get started by writing individual AIs first and then expanding them to include group stuff.

One method, by the way, is to have an AI entity representing the group's invisible leader. That leader generates higher level goals and then passes orders down to the individuals. The leader doesn't really exist but rather represents the group training that they have together.

For some insight on how to implement Squad AI you could check out van der Sterren's and Reynold's articles in the first AI Wisdom book, also the paper "Behaviour Representation and Simulation for Military Operations on Urbanized Terrain" by Shen and Zhou.

thnx, I'll take a look at those

AI Game Dev has a great collection of info. Also FEAR is a bit old now, but people still think it has good AI, so Jeff Orkin's page might be useful as well.