How do you know what a stinging plant looks like?

I live in florida if that helps you identify. I think the plant is called a "fire thistle", Im not sure. I thought it was a nettle but maybe not. Anyways, I can't walk in my backyard without wearing shoes, and I'd rather just pull the plant out. But the thing is there are a lot of small plants, so I can't tell which is which. What does it look like so I can pull it out?