They come in all shapes and sizes.
Just write the pertinent information on a piece of paper and you’re good.
Trust me— whatever you write can’t be worse than some of the one’s I’ve seen. Just keep it looking neat and clear.
If you want to know what to PUT ON, that’s a different story altogether. There it’s pretty much whatever you want, though there are basic guidelines like name (obviously), age, birthday, personal description (physical and character, can be short), schools attended (high, sem/ yeshiva gedola and college), shul, brief parent info, what you’re looking for, and a reference or two. That’s pretty much bare-bones. You can really put whatever you want on.
You may also need a pic if you’re a girl, unfortunately. Don’t supply unless it’s requested. Many people won’t request it, so why send it if you can avoid it?