If the ants like sugar, Terro is good and if they like protein, a protein bait is needed. The bait comes in little plastic disks that are easy to put where the ants come in and in liquid form.
I really don't know where they come from. Check cracks, like if you have a carpet, check between the carpet and the wall. Or just try and look where there might be an opening in the wall. But my brother had the same problem the other day. A good way to get rid of them is to spray Pine Sol especially where they are mostly at. My brother has seen less ants in his room. Ants hate the smell of Pine Sol.
And you can also try those ant traps that have bait. Yes, it will increase the number of ants but they will take it to their queen and it will kill them.
I cleaned my room just yesterday and wiped everything down, and there is no food or dishes in my room. I found them under my pillow and under my playstation. Where do they come from? Why do I have them? and how do I get rid of them? :'(