Through April 1, every $50 spent using your "SEN Wallet" gets you $10 back. That's fancy talk for putting money into your PSN account and spending it. Sony has a list of suggestions on the PlayStation Blog, including pre-orders of MLB The Show 13, BioShock Infinite, and more, but any purchase adding up to $50 will do.
This is a really great time to get a year of PlayStation Plus and start loading up on all the included games, especially with an extra three months added to your order through March 4 – though as that costs $49.99, you might have to top up with, like, an avatar.