Personally, I've found that for a "low" spender (< $1k/mo) on the actual credit card, most cards won't give you anything too significant. Even the special 2% cashback cards (citi double, fidelity amex, etc.) are talking ~$240/yr or less (obviously depends on your spending, but this would be it for a $12k/yr spender). It's good for a little icing on the cake, but let's be honest, not many people get really excited about that small amount of money. But hey, if you do, then go for it!
Personally, I've probably tried a new card every year or so since I turned 18, and recently settled on the capital one quicksilver. No fee and 1.5% cashback on everything, Visa so accepted everywhere, and no foreign fees. Apart from that, it's just one less thing I have to think about. I get offers periodically, but it's just annoying to go out and have to play games to manufacture a few hundred dollars in bonuses by churning cards. It can work well if you enjoy it in some way, but you have to judge whether the effort is worthwhile. I think I average around $1k/month on my credit card for a full yr.
I'm lazy, so prefer convenience. If I had a huge trip or something, I may consider a new card for a quick bonus, but otherwise not very helpful... in my personal case.