First you ask:
"Is this ringworm?"
The answer is:
If it's red, itchy, potentially flaky, and forms a roughly circular pattern, the answer is a definitive "probably." It may start as something the size of a pencil eraser, but can grow in size fairly quickly if not treated. If you still need convincing, do a Google search for "ringworm images" or something like that. Be prepared to see people with cases that are typically much worse and more poorly photographed than your own. I mean, "worse than the case of the person that you're doing this research for."

Next you ask:
"Well how the (insert favorite modifier) did I get it?"
The answer is:
This condition is an outward manifestation of something embarrassing and shameful you did and aren't telling anyone. You itch because you're evil. If this isn't the case for you, it's because you have a fungus that's feeding on your dead skin cells, which you likely picked up due to casual contact with an infected person (who you may rightly suspect has done something shameful), or a surface that has been contaminated.

Then you logically wonder:
"What am I supposed to do about it?"
The answer is:
Don't scratch it. Remember how you got it just by brushing up against something? Yeah. That means that it's really contagious, even to yourself. Have it on your leg? Arm? Under your fingernails? That's tinea corporis, or ringworm of the body. You can also get it on your scalp (capitus), hands (manuus), feet (pedis), face (faciei), and groin (cruris), among others. Go to a pharmacy or grocery store or department store or pretty much anywhere that sells hygiene products. Find some cream that mentions the kind of tinea you have, and tell the cashier that it's for your grandpa. Be diligent with it. You'll probably have to apply the cream once or twice a day for about 4 weeks. Just do what the tube tells you (not to be confused with the television, which may give conflicting advice on unrelated subjects). It's a pain, but you'll feel better once it's gone (the rash, not the TV).
As a side note, I've recently become aware of a product called "neem oil," which should be a great alternative for all you sandals-wearing, organic medicine-loving hippies out there. Or maybe you're just allergic to tolnaftate. Who cares. Supposedly it works very well, and more quickly than non-organic alternatives. But let's be honest: can we really trust nature? The same nature that gave you ringworm? In addition, to the benefit of your dignity, your fellow students and co-workers currently have no idea what you're going through. Neem oil's strong, pungent smell will "out" you in no time. But if you still want to use neem oil, you'll be glad to know that it also allegedly works as a pesticide, skin conditioner, hair regrowth tonic, toothpaste, and a male birth control product. Yeah.

Finally it occurs to you:
"I don't ever want to get this again."
No wonder. Try this:
Forget about it. There isn't much you can do as far as die-hard prevention, aside from the things that you should already be doing. Keep yourself clean. Bathe regularly and thoroughly. Change towels frequently. Don't wear dirty clothes. Change your socks daily. If you use a gym shower, wear sandals and bring your own soap. Don't rub your face on any part of another person that you suspect to be infected. Toilet seats? Hoo boy. Those things should be illegal anyway. Raw or broken skin is more likely to become infected, so keep your skin healthy and dry, and avoid knife fights.

Hey, it's only ringworm. Thank God you're not a squirrel with a botfly larvae infestation. And while you're thanking Him, apologize for all those horrible things you apparently did.

Feel free to thank or curse me for taking the time to amass all this information for you.