Create an interesting map, place some AI entities in it, and run it. Don't kill them straight away but turn on mat_wireframe and watch their actions as you move around. You'll see them, more or less, run straight at you and shoot. This is because they have no bearings in the world other than your position.
Leave the game and lay down info_node entities across the map (what is the optimum density?) then recompile and do the same as last time. You should now see them group and attack together if they need to, seek cover, throw grenades at far more suitable times, try to get around you and more - all because you added a few nodes.
This alone has fully set up your AI for a map.