When I'm dating I talk to multiple girls and take them out etc. I personally do not have sex with the females I'm dating but if it ends up happening it shouldn't be a problem, even if I happen to just tell the other girls I'm dating.

Now I usually end the dating phase and go with the girl that holds out the longest and I have more of a "connection" with. GF/BF stage is more commited and you have plans of the future together.