You've been given some solid information but I'm going to shatter your world a bit in that "busking" can work against you in some instances, but especially if you're shooting for legit paid gigs. Given your age and circumstances I'd find a local family dining facility be it a pizza joint (locally owned, not a big chain store) or a place like Red Robin or one of the big Buffet chains. Talk to the manager and tell him that you would like the opportunity to come in a few nights a week to do table-side magic and ask if it would be ok to put some brochures at or near the check-out that tell folks about hiring you "In-House" for private parties. Understand, you are offering to sell a service from which their business benefits -- the private parties, be it a birthday party of anniversary means sales of product so chances are in your favor they'll go for it.
Dress nice and be well groomed when you approach the facility and when you work! Make especially sure that you have fresh breath.
If at all possible, get yourself a simple web site up and set in a style that can easily match the art design features used in your business cards, letter-head (real or in your eMail. . .consistency is the key to creating a "brand" around yourself). You don't need to pay a fortune for them, but have some nice photos of you on the web site and where possible, action shots of you working on the street, in an eatery and someone's living room . . . you may need to stage some of these shots with people you know (make sure to use different people however, when it comes to each setting).
Your web site is an electronic brochure and because of your age, it doesn't have to be fancy or over-done. In fact, you will hurt yourself if you go too over the top with the flash and whistles... KEEP IT SIMPLE . . . you're young and it's perfectly fine.
If you have a deal with a location don't forget to plug them in your physical brochure as well as on the web page -- make them your friend!
Get quotes! People that have VIP status are always excellent for a line or two, but start with general reactions from people that watch you. Get their name, age, etc so you can credit them to the quote and the event, their position in life, etc.
I've jumped around a bit but I think I've shared some reasonable perspectives;
1.) Get the Location -- it's ok to work for tips or a nominal mode of compensation for now; say $20.00 a shift + food/meal credits and personal sodas.
2.) Create a Market Presence & Brand -- this refers to your physical brochure as well as the Web Site and Business Cards. You want to maintain consistency of appearance, fonts & style so that people can readily recognize you and not get you confused with other magicians in your region.
3.) Have Your Product Ready -- (which should probably be your starting point). . . You need at least 3 10-minute close-up sets that can rotate as you work the tables, each being easily re-set so you can keep moving. You also need two types of floor shows; one for the kiddies (which will be your bigger market) and one for adults. If you don't have these things, you can't sell them. . . and remember, Card Tricks don't work on little kids; you need fun, easy to follow and yes, "silly" schtick. It may not be what you want to do but it is what makes the money and builds your reputation.
Your "adult" show should not be crass or even slightly naughty in that it will work against you because of your age. Delivering well rehearsed, solid routines such as Rope Magic, Manipulation work with coins/billiard balls, silks, etc. or a variation to such work. Use large sized playing card sets for hustle routines such as the old Sidewalk Shuffle as well as classic gags like the Six Card Repeat. Think of it as the fun adventures of young magicians finding his way in the world . . . .
4.) Be Ready for Rejection! Believe it or not, there are a lot of people in the world that don't like magic and are especially disgusted when it comes to card effects. There are two primary reasons for this; bad/rude performers and the ego-based frustrations of lay people because they can't figure it out. Business wise, some proprietors (in fact, many people in general) still see magic as something for the kids but that's why I suggested family restaurants. But even when it's free, people will have objections and it is something we must be ready to deal with. . . the UCLA Business School actually offered a course on this subject and on failure in business because statistically, these are far more common than success. Learning how to use those experiences however, is what helps you grow professionally and vocationally, so just learn to not take it personal and hang in there.
That's pretty much it.