I guess don't act creepy/sneaky.
I'm assuming a lot of times this happens when it's a crowd where the girl or girls will pose or dance while a bunch of random people (guys) would whip out their phone to take the pictures. You're in a group, there are probably others more creepy than you so take your picture no problem cause you have camouflage.
On the other hand maybe when you are the only one with the camera. Walk in front of her, give her a nod or a wave and signal (or ask if you are close enough for her to hear you) you want to take a picture of her with your camera. If she is reciprocal she'd smile and do a pose. Snap your picture or two, signal a thank you, nod, smile and on you go. Lingering too long makes it creepy tho.
