How to find the best deal on a room at the mgm grand las vegas in may?

I usually find that working directly with them, either on phone or on their website – gives me the best deal. The website will show some promos, that may give you some goodies along with your room. Such as free drinks, casino chips, free dinner or buffet, etc.
You can also check the other sites like hotels.com and hotwire – but if you book through them, I have learned that if there is a screw up when you arrive, MGM’s hands are tied as far as helping you.
Hint: If you book through MGM – keep checking room rates on their website, because they can go down after you book – if they have an abundance of available rooms as time goes on. In that case, you can cancel your existing, and then rebook at the new rate.