Help with sister

ok /lounge heres my problem, im 18 and my sister is 25. she lives far away from me and comes to visit rarely. she is truly gorgeous and she is always the object of my masturbation.i still live with my mother. any tips on how to seduce her?
btw she is only half sister

im only 18, cant buy alcohol
and she only comes out very rarely to the house i live in with my mom

and also its her tits that are magnificent, too bad i cant see em bare