What do I need to do if my macbook pro is extremely slow?

I got my macbook pro this past july and for the past week it has been acting extremely slow and I'm not sure what to do. I asked one of my friends with a mac what I should do and she said that I needed to delete my browser history, delete my cookies, and empty my trash can. Well after I did all that it's still being extremely slow and I dont know what to do. I'm supposed to be acceting a call from apple support tonight around 10 but I was wondering if there was anything else that I could do. Any suggestions?