I was wondering how young a puppy could go into heat? what are signs that she is in heat? she has been acting real weird and after a nap, she wakes up and there is a clear (almost like snot) hanging from her vagina....anyone have any idea what this is?

How old is your pup?
Females go into heat after they have reached adult height and weight, depending on the breed the age can range anywhere from 6months-24 month. Every dog, bloodline, breed is different.
If your pup doesn't meet any of these age specifications I'd be giving the vet a call just to be safe.
Is there any odor to the "snot"?

she is a 15 week old lab.............i don't check to see if there was an odor to it or not.......just was really digusting and though it was a one time thing but saw her with it like 3 times............

Six months is the youngest I have heard of. She is not even four months old, I think she is too young, and THAT does not sound like a heat cycle. Better get her to the vet.

i am.....she has an appointment today