I recommend:
1. A reputable brand, whether something smaller like Micro Center branded cards or a well-known manufacturer like SanDisk or Samsung.
2. A minimum, Class 4 card. Depends on usage though, if its just to store photos and music, it'll work great. If you're one to throw HD video recording and move large amounts of data on and off, like a heavy app, you may want to upgrade to a Class 6 or 10.
3. Choose your capacity. It's up to you.