There's a method that people with long hair frequently use called "dusting". Ideally you want to use a pair of actual hair cutting scissors, or stylist's scissors, but if you're short on cash, just make sure they're really really sharp. Sit down, and take a good look at your hair. When you find a split end, cut that hair, and that hair only, just above the split. This method takes more time, since you're going to have to hunt down the split ends one by one. But, it won't do anything to change the length of your hair, and won't affect the hairstyle you have. It's the safest way to get rid of the split ends, without risking a bad self-haircut.
If you want more information, there are a number of really great resources out there for women and men with long hair. They can help.
Also, make sure that the ends of your hair aren't dry. Toss a little leave in conditioner in, or a hydrating treatment if you can. If you can't and money is tight, go to the kitchen and put some plain old olive oil on the ends of your hair. Put your hair up in a bun, and leave it for a few hours, before washing it out. It'll keep the ends from looking as frizzy, and will hide some of the split ends.