I am a sophomore and have been doing magic since I was six. I would recommend doing self-working tricks that even the most suspicious heckler can't ruin. Given your age, you should probably check out John Tremaine's Magic and card tricks, a book that includes many tricks that work themselves and require little or no SOH. Things like the two-card monte are great, but only if peformed flawlessly, or close to it. Plus, spectators are quite unpredictable. If they suspect even the slightest thing they will grap at your apparatus or, the mother of all effect ruiners, look n their hand/turn their hand over.
While on that subject, here is what I say to try and avoid that:
-"Make sure NO ONE can see those cards"
-Explain how 3 Card monte is played, without looking at the cards, and say we are going to do the same.
-Tell them, while doing the fast switch, that at the end they are going to have to guess at the location of the cards.
-Tell them outright that, if they try only to ruin the trick, then they ruin it for themselves, for the audience, and for yourself.
I hope this helps. BTW, the first time I performed the two-card monte, I was 13. The girl turned her hand over and ruined it for herself and for me. I was so embarassed that I waited a whole year before attempting it again
Hope this helps, at least a little
Sorry for the length, but I like being quite descriptive in my writing.
May all your days be Magical,