asking what moves to use for Mew is a lot like asking what Pokemon make the best team, you will get a differant anwser almost every time. but, since you asked, i'd use:
- Psychic (a must have for any Psychic Type)
- Earthquake (for taking out any pesky Steel Types)
- Toxic (use it as your first attack and the damage really adds up)
- Rest (i shouldn't have to explain this one)
hope this helps!