Experiance.
The fact is you need to find something that makes you interesting, you have that in the survey. A simple opener is "Hey, I'm doing a college paper. I was wondering if I could interview you for it because you seem like the kind of person it's about." Whilst your interviewing, just make conversation, like "So, you been interviewed before? No, well I haven't done this before either. Was it as good for you as it was for me?"
The more approaches you make the more you'll be able to cope with them walking off and see it really doesn't matter. I conquered my fear of rejection when I asked the girl I most fancied out, she turned me down in a nice way and then made her excuses. I still talked to her afterwards, and in fact I think she rather likes me, but I haven't seen her in months. The thing is after I was blown off, the pressure came off and I started acting more real. Once you have the pressure off you'll feel the same.
If you want their number as well, start with that as well. Just look at them and say, "Woah, you're hot. Sorry, I just had to say it. I'm doing a college paper about relationships, can I survey you? It's just like Family Fortunes."