As cam sex is a very modern thing, it has just about 10-15 years experience, it's yet developing and no one could say definitely which rules it has and what way it will be in future.
The most usual cam sex with a cam girl consists of mutual masturbation with client during c2c (camera to camera) and sexy talking. Most guys like to watch cam girl playing with herself, speaking in sexy manner and showing her their hard penis.
Also it's quite often cam girl's customer has some special request during the show. It could be strip tease, using dildo, anal plug, lovense play, blowjob,
deepthroat, toilet games, role play including incest, joi (jerk off instructions), cei (cum eating instructions) and many other requests.
There could be really odd and rare things which customer can ask from cam girl, for example pick her nose, open her wardrobe ect.
Cam girl could be also a good friend to chat to, a girlfriend online, a good psychologist to turn to, a funny way to spend time, using also whatsapp and snapchat for sexy talking, exchanging photos and videos and play online.