You need something in your room that you can ask if she wants to see/do/play with/whatever so that you both have an excuse to go up to the room even though you both know whats going to happen. this way you can allow her to say "we went to his room for -blah- and then it just happened"
I personally have a laughing gas dispenser in my room - theres nothing better than doing a little nos with a girl (and because you can say "make sure you are comfy" before the balloon they always get on the bed ;D )
also making out after a nos balloon is amazing and seriously gets girls wet if they did it right
good luck bro