OutThere - the trick is to do enough emailing/texting so they're not a complete stranger, you feel like you at least want to meet them, but not enough that you have unrealistic expectations when you do meet.
A few other general rules of thumb (there are exceptions to all of these, but generally):
Always believe the worst photo. If they only have one, they won't look as good as that in the flesh
People are always funnier & wittier when behind a keyboard. Don't think you know them until you've met them two or three times in person.
Sometimes things can go well and then people drop off the radar. It's very unlikely to be your fault, if they do the disappearing, it's for some unknown reason. It's tough to deal with at first, especially if you like them, but it happens.
Keep an eye out for the red flags, only meet those you really want to meet - those who you are thinking 'meh' about probably won't be better in the flesh
Remember they're meeting a complete stranger too, you can joke a bit about how weird it is with them, and see how that goes down. If they're serial daters (oh I do this every week) then that's probably a red flag right there. Have a get-out clause ready if you need it.
Don't drink alcohol, or at least too much, on the first date
right. I've applied for a job. That was quick. yay me