credit cards

i have been thinking of using one of my cards i have not used solely for work. just to separate the work related expenses and so when i send over my bill to australia my boss will not see my personal expenses. im still not sure on what to do because i can also sign up for a new card. i have been checking on what cards are available right now because i really want to get the Best Reward Credit Cards. i want to make sure i earn points, rebates or rewards. or atleast i get a credit card that would give me a low interest rate. decisions, decisions.