First off, you should be responsible with what you are waxing. Ideally, it would be something that you own, or have permission to wax. Such as, your own skate rail, or the curb in front of your own house. If you wax public rails and curbs and what not, people can get really angry. you might not care about that, but if these people get angry enough, they'll put up skate blockers (those little blocks or walls that get welded into place on rails to keep you from skating them). Skate blockers suck, and honestly I don't understand how they are even legal (aren't they trying to injure skaters?!?), but all that aside, they do ruin cool skate spots. So, be responsible with your waxing. Use reasonable amounts, and don't be the jerk who ruins a great spot for everyone else.
How to wax
Skate shops sell pro skate wax, and that stuff works great, but if you are poor you can use all kinds of other stuff. Like, for example, a clump of wax from the grocery store. Or a candle. Be creative. Soap can even work (though not as well), and it has the bonus of washing away. You can tell people you're cleaning up the neighborhood.The point of waxing is to have a smooth, even surface down the whole object. You don't want it patchy, and you don't want a super slick surface - that ends up being dangerous. When you first apply wax, put on just a little and add more if you need it. It's always easier to add wax later than to scrape off extra wax. After waxing, rub your board along the obstacle, pressing down hard to see how slick it feels to see if you have enough. Rough curbs will need more wax than rails.

