The romantic belly raspberry must be done carefully. In an intimate moment, gently kiss the belly, then perform the raspberry. This is a tremendous tension breaker, and has the advantage of relaxing the recipient. Warning, though, some people are turned off by all forms of raspberries. To minimize damages, try to keep the raspberry short and moderately dry if this is a first time with a partner. The sensation produced isn't enormously erotic, but rather tickles pleasantly.
Never perform this manoeuvre on a woman in a bathing suit unless you have discussed it beforehand.
The pet belly raspberry should not be performed in public. However, there is no shame in secretly raspberrying a dog or rodent pet. Do not attempt on a cat, or a hamster, and especially not on birds. Most animals that enjoy a belly rub will enjoy the belly raspberry. (Pet rats really enjoy this.)