digging the nails into your guys back is a maybe.. every guy is different, one mite like it, and another might not.. but something that all guys like is if a girl is tight. so one thing u can do for him.. and yourself actually is to do your kegels.. its the same muscle you use to pee.. flex that muscle often, just like you would for any other workout regimen and youll be super tight and hell love it.. especially if you flex these muscles while hes inside of you.
(also try reverse cowgirl.. they like it because they dont really have to do any work haha and they get a really nice view of your butt)