1. If you're 16 or 17 in an area with poor public transport and parents who would, understandably, not be too trilled at possibly half an hour to drop their kid to work, half an hour home, and then repeating for picking them up... actually forget that. If you want a job, forget about your other circumstances (schooling, transport or lack thereof, effect on others in your household) and do something ridiculously inconvenient because anything else is the easy way out.
2. McDonalds is certainly not the only job going around, but it does have a very good reputation with regards to teamwork, etc., especially when people are going for other part time or casual work in an area such as fast food or retail (which most students will end up in throughout their school and university lives because it works well with regards to their other circumstances). But wait... Drop out of your degree and find something else, because no one should work in fast food (ignoring the fact that plenty of people eat it, which means that someone should work there so they can continue to do so).
3. When you're just getting by as a high school or university student (I'm talking about one who is living at home), it gets to a point where you want your own money rather than asking parents for it all the time. It's a kind of "paying the bills" mentality, where you're doing what you can to get by in a social sense (usually) while working towards something else (presumably through high school or completing a degree). Actually... just give up your social life, since you're just being lazy by taking a job that's convenient and allows you to have that bit of financial freedom that you want.
In short, I completely agree with wuddie, despite all logic that suggests that I shouldn't.
