Who of you gentlemen was able to make a woman reach an orgasm by touching only her breasts?
For starters, she needs to feel comfortable and safe. It's almost impossible for a woman to enjoy it if you are not able to make her feel safe and comfortable in your presence. Bringing a woman orgasmic pleasure is indeed a life skill.
So before you start pressing, licking and sucking the breasts of your partner, thinking that those actions will make her tremble with pleasure, first you need to worry about the preliminary, which serves as fuel for sex.
It is hard to imagine a woman who's not warmed up yet, to enjoy a few quick and fast motions over her breasts. Now, if we think that she's already been brought to a good preliminary stage and she's getting crazy with lust and horny, with her barely being able to hold up her eyes open, don't you think it's easier to consider that playing with her breasts at this point can bring her to orgasm?
Remember... the breasts are very sensitive and if touched the wrong way, can cause discomfort and pain.
So, first of all, take it easy, starting with a very light touch with soft and slow licking. The pace should increase and intensifie as you sense the response from your partner. Oh, and don't forget, it's all about circular movements.
Now you just need to practice and get her to a point that you can control and enjoy the experience along side her.