You will generally need some rapport to get a photo(s). Showing the girl the shots and letting her choose which ones she likes and others she wants deleted can help enormously.
Respect girl's privacy if she says no. If she is not advertising with photos of her face respect that too unless you have permission to post her on sex site (mute point really, how can anyone know if this is really the case?). Pics can be taken at angle to not show full face, or you can pixelate to disguise yet still show the girl is beautiful.
It's between you and the girl, I would never ask the papasan/mamasan .... it's none of their business and they may just say no, or ask for extra money, exploit girl, etc.
Sneak photos are discouraged, it's pretty easy for us to see if a girl knows her photo is being taken or not. Posting other Bros photos without acknowledgement, or fake posts/photos is a slippery slope you don't want to go down.
Extreme hard core shots are not that well received, showing all the girl's assets in a tasteful way is okay. If you have the right to set RA30 or so things are more open .... if not, it's encouraged to PM the section mods (via "report") to set an RA for you. Be clear what pics you would prefer RA versus no RA, they don't have to be all set at the same level and it can be good to have some of the more innocent ones in a set left unrestricted.
NB the mods reserve the right to set RA or delete any photos posted .... this will usually be after some mod discussion. You may find your thread moved temporarily to the mod section whilst this discussion takes place.
Pics without a meaningful report can be pretty ho-hum.