I have a system these days:
I use my Discover card almost exclusively, and I rack up the cashback bonus as time goes on. Now, you can redeem it for cash, use it to pay down your bill, etc., but if you look around Discover's website they give you the option to get even more value by spending it on gift cards from retail partners. You can spend $20 on a $25 gift card to Banana Republic, for instance, get yourself a pair of chinos. Sometimes you can even get double what you spend, like $20 for a $40 cert from FTD or 1-800-flowers (a smart move on Valentine's day).
Turns out one of their partners is Guitar Center. Not the best deal out there, but $90 for a $100 gift card isn't bad, and since it's paid for from your cashback balance it's basically free money.
Then I wait for a good deal at GC and strike. That's how I got my SE Angelus: $150 off plus $600 in gift cards, and I took home the best acoustic I've ever owned for $50 plus tax. Which makes my wife happy.