If you really are single in the truest sense of the word, you won't need contraception...as long as you're not likely to have sex outside of a relationship, that is! It goes without saying that if you don't have sex you can't get pregnant, so abstinence is still the most reliable way of avoiding an unwanted pregnancy!
And when you meet someone special? Condoms are a must until you've both been tested for sexually transmitted diseases (AIDS, at the very least). The Pill is more effective than just using condoms, and the Mini-pill can be started at any time (ie you don't have to wait for your next period before you start taking it), BUT you must use a condom for the first 7 days (or abstain from sex during that time). You could also try the coil or implant, as long as you're not planning on having a baby any time soon.