I'm 21. I used to be shy about the idea too. I still am in public and even online, and haven't actually tickled or have been tickled by anyone other than my girlfriend (off-line). I just recently went to visit her and alot of the time was spent physically together whether it be at the movies, the mall, or my hotel room, which was the point. We'd just lay there and hug and hold eachother, and make out sometimes (in my hotel room this happened, the heavier stuff that is).
I wanted to tickle her as I've never really got a real chance to do this before in real life. Her and I roleplay online and I tickle her as a tease for teasing me about whatever I may have said that was silly or funny or whatever it might be, so shes used to the idea and doesn't mind it.
Naturally when I first met her (on this trip I took) tickling was quite a natural and fun thing to do with her. While it wasn't the focus of the togetherness it was fun and entertaining when we did do it. We'd wrestle eachother and pin eachother playfully, and then I'd tickler her and she'd tickle me.
This was truely my first experience in tickling and neither of us felt embarassed, ashamed, or shy about it.
Although she is a very understanding person. While she doesn't personally have a fetish that I know of for tickling or anything else, she thinks its cute of me to be like this and she likes the attention I give her in this way also, and I'm more than happy to give it to her when I feel like it.
The key is to not wear it out though or focus on or think about just tickling. Too much tickling can be a bad thing and your girlfriend or prospective girlfriend might think your weird or obsessive. Try to keep it as an option rather than a must. I'm not fully into my tickling fetish if you can call it that(hell, this was my first time indulging). It was just another way for us to express our love for eachother. I wouldn't even call it a fetish in this context. Intimate, yet playful. ^__^
Anyways, I think you should just go for it like Krokus suggested. While you might want to question her about it first, don't give her the third degree, explain too much, or get paranoid about it. If you tickle her and she doesn't like it, then you'll know to stop. She may be lying so as to not be tickled again, or she may truely not like it at all. I'd suggest then talking to her about it more fully. Also, the moment and the place has to be right. I don't believe tickling can be productive for a relationship if its done with exposure. Depending on how you would plan or want to tickle her, I'd suggest doing it in private, so as to not embarass her or yourself.
If you want her to like it, you have to let her know shes in control of the whole thing and that you'll stop when she wants you to. Use your best judgement and your gut instinct. Theres a chance she might not even be ticklish and is merely laughing and squirming to make you happy. If you suspect this there are ways you can tell, pretty much.
I know my girlfriend is ticklish because I've asked her prior, before I even met her if she was, and she said she was. When I tickled her sides and back I found her reactions were stronger in this area, and if she had been faking it I would have known. She was trying desperately to get out of it and there was just a vibe validating the whole thing. You will know.
The best advice I can give you though is to be totally honest and truthful with her. Don't tell her half-truths, and tell her about how you feel and try to explain it in a way she could relate to. Make sure not to seem obsessive or go into too much detail about your fetish (or whatever it is you feel you have). Let her ask those heavier questions. After an honest tickling, she'll probably have questions of her own, and it will probably be at this point that you and her will break ground and actually talk about it. And it is in this moment that you will probably feel at your best and most comfortable stance when talking about it with her.
If she doesn't like the way your doing it or she feels uncomfortable talk to her about it. There are ways to find mid-ground without having to sacrifice tickling her altogether. Provided shes understanding, she probably wouldn't mind the tickling at all as long as its not overdone or done on an impulse when the situation isn't right.
Finally, let her experiment with you too. Tickling goes full-circle and she may get equal enjoyment out of it(as well as understand it) if your both trading off now and again. She probably needs to feel shes making you feel good about it the way she is making you feel good about tickling her. You both need to be comfortable with eachother, and sharing the in tickling is a good way to establish tickling as an exercise or practice in your relationship.
P.S- I'm speaking from personal experience and am talking in regards to a serious, real romantic relationship.
If you want a more broad perspective, or your just asking for comments or advice about tickling your female friends in general then just go for it. I spoke in the interest of establishing a bond and connection. If you meant for this to be dealt with as more of a 'passtime' or casual thing, then go ahead and just tickle them when you feel you want to or need to. If they don't like it, stop. If they don't like the way your tickling them, change it. Your friends are your friends, they'll tell you whats wrong directly.
If your looking to become intimate with them however, consider more their personal feelings and actually talk about the subject, and what it means to you. If they think your weird because of it, or don't take you seriously, don't let it discourage you. You'll find someone who either thinks its cute, doesn't mind it, or likes it as well, or all three. 🙂
Remember though to keep the tickling in its place. Don't let it take a commanding presense in the relationship. You need to focus on equally or more important things and establish bonds first. Once you've done that she will probably be more likely to accept any part of you and will accept you in whole as the wonderful person that you are. 🙂
