How can I train my 3 month old puppy to give me some sort of signal when she has to go...
I know she knows not to go in the house but she will if I don't realize she needs to go and get her outside in time...not that it matters but we she has to go down some stairs to get to the door.

If your puppy has accidents, then she doesn't know not to go in the house. She isn't potty trained yet. First, you should crate train her and keep her in the crate any time you cannot constantly keep your eyes on her. Even if you were to train her to give you some kind of signal, she'd still have accidents right now. Crate training is the best and easiest way to prevent accidents and potty train her.
here's how and why to do it: http://www.leerburg.com/housebrk.htm & http://www.leerburg.com/qahouse.htm

The best trick i ever learned (and am thankful for to this day) is the bell. Get a small bell from a craft store or wherever, and hang it on a string to a level your pup can reach it with their nose. every time you go to take them outside, say "outside" (or whatever your cue is) and ring the bell. then take them out. it won't take long for the pup to figure out that ringing the bell means go outside, and they'll start nudging it themselves. However, be warned that they also will ring it just because they want to go out, not just when they need to. Just make sure in the beginning to take them out every time they ring it, and encourage them to go. if they don't, right back inside to the crate or wherever and try again in a little while. hopefully they will figure out soon that if they ring the bell, they need to "go", otherwise they get put back up.

three months is plenty young to expect complete housetraining behavior, but the bell might be the cue you're looking for. And it's never to soon to try or to start the learning process.

good luck.

I must admit that bell training works well. I had a dog "train me" with it- they will ring it for everything after they figure out that you come to them to take them out when they ring it! She would ring the bell and as I would come into the room she'd have her toy in mouth and play bow before running full blast at me to play. Potty time? Yeah right... But she did use it whenever she had to potty also. It's an option, but you should still crate train also. It will really help.

Thanks for all of your responses. I am crate training her. Unfortunately she is probablly out a little more than she should be because of my son wanting to play with her...and I feel guilty. (She hasnt had a lot of accidents)
She does know "outside" and when we get outside I tell her to go potty and she does...I will definately get a bell ...I think if I could give her a way to better communicate to me she needs to go out it will help things...she has actually gone toward the stairs but...she won't actually go downstairs or stay by the stairs for more than a second so its easy to miss. I have the video 8weeks to 8months and I understand keeping your eyes on them at all times...so my fault for letting her stay out when I leave the room even for a second..I know.

I too have successfully trained 5 dogs with a bell on the door handles. We have them on all the doors at our house that go outside. It really helps when we are upstairs or in another room and cannot see the dogs waiting at the door. I don't think it's ever taken any of them more than a week or so to learn that's what it means. And make sure you reinforce this behavior with a lot of positive praise, this makes a tremendous difference.

What cracks me up is when my 2 pups are playing and one of them will suddenly jump up with this "Omigod, I gotta go NOW!" look on his face, run to the door and PING!!! Smack that bell so hard it goes flying across the room!