Yep, we have had several threads on getting the ideal credit cards. Typically the signup bonus is the biggest reward you can reasonably get per $ spent.
Younger people often have trouble getting the "first" credit card. If you can get someone like a parent (who is 100% responsible with credit!) to add you as an authorized user, that gives you a leg up starting a credit history. Choose a Visa or MC, and you actually inherit their account age as well. That credit card will show up on your credit report. If the card has always been paid on time, it's a big starter benefit - especially if it's several years old. If the person has NOT been responsible with credit, it will be BAD for your credit history.
Easy-ish cards to start off with are Discover or the Chase Freedom, both of which can give you a small signup bonus. Freedom usually has the bigger bonus ($100-$150) and if you have one card with a good history on your credit report, Chase will very likely issue it to you.
If you don't have a parent to give you a leg up, you can often get a starter credit card while in college (some companies ignore your lack of credit history if you are in college and target getting you your first card) - otherwise, you may have to look for a "Secured" credit card.