I have many, but only use 2. One for everyday purchases, the other is on my husbands paypal account. I pay mine off every month plus I get cash back-that really is the only reason I use them.
When we moved we got rid of around 10 and it took my credit score down by around 100 points-so I decided to keep the rest. I check my credit report once every 4 months. My husband says I am anal, but my sister had her identity stolen and it caused her lots of problems so I probably am.

Actually i dont have any credit card till now but in future i may have it.

Id say 3

1- I use for my work at home business
www.rockhardbody.net
2- personal purchase such as gas, food, clothes
3- My primary business

Its great to keep these seperate it makes book keeping much easier