In terms of CIS, CCCA teams, I would offer these hints:
1) Email the head coaches of the schools you are interested in. Introduce yourself, provide some background/brief stats, etc. (Their email addresses are usually on the team webpage.)
2) Once you know your high school team's schedule for your senior year, send it to the schools you most want to play at. If your team is playing nearby the school you are interested in, suggest the university coach come out to check out your game.
3) Have somebody videotape you in game action. Be sure to get video of defence, rebounding and hustle examples as well as what you do offensively. Once you have compiled this video, edit it down to manageable clips and string those together so that coaches don't have to wade through hours of video to see what you want them to see. They don't want mixtapes, necessarily, but instead clips that show what you can do in context of the larger game. You can put that video on a private YouTube channel and send the link to coaches.
4) When coaches do come to see you, talk to them. Ask them questions.
5) Be honest with coaches and don't play them against each other.
In terms of NCAA schools, attention is more difficult to attract. I'll leave that up to somebody who has more knowledge.