1) Don't listen to a girl's words, listen to their actions. They will tell you stop but let you rub their pussy. Do not rape them obviously, but identify the difference between token and real resistance and always continue if she is still there enjoying your company.
2) Don't ask her, just put a condom on. Asking her a question will autopilot a 'No' response by nature.
3) If she let's you rub her on the outside but not the inside, take her hand and rub her own pussy with it. This is my magic arousal secret. Rub her to the point that she goes crazy for you and then you can take over with your hand.
4) Don't neglect the nipples, ears and neck. Often I will pull on the nips whilst making-out with her neck and ears, whilst my leg is inbetween her legs rubbing her indirectly whilst whispering her ear 'Feel good, doesn;t it?'. - Really work MULTIPLE arousal zones simultaneously. Do this for like a half hour. Her pussy is usually gushing when I eventually make a move for it. There is no rush.
5) Put their hand on your cock, some girls get even more turned on by sucking your dick. (YEAH REALLY) That in itself can blast through the LMR, but they will not always grab your shlong. Feed it to her as you're turning her on and then she will have some nice play time with it.
Some concerns:
- Is she a virgin?
- Is she on her period?
Girl's won't tell you till you encourage her to respond.
This might sound chodey, but it works, tell her 'You don't find me attractive, do you?

' and she will probably tell you the real reason so you know what to do after. This actually works since I know she is into me at this point lol.