Don't you think it's always best to say something like "u ready" or "wanna have sex now" just before having sex, and putting a condom on? Like if you're making out and doing foreplay, how will you know for sure wether to slip a condom on or not to have sex?
Should you say somethin like "do you have protection" to give a hint or what?
For a first time with a girl, you kind of need to ask them before you start climbing on board. A simple "Can we put on a condom on now?" might suffice.
I agree Magnetic but also remember that you cannot rush into things like this. Make sure that you have got a good relationship before start trying to get access to her knickers