Okay, so, there are really two options for teaching ESL in Switzerland (or anywhere, for that matter). Option 1 is to teach English to school-age children. This has been covered in posts above, and I'm no expert on teaching to minors (can't stand the little so-and-sos, to be quite honest). Option 2 is to teach to adults, which is what I do here in Switzerland. The following is my advice based on the whole 6 months of experience I've gained so far:
First off, getting a job teaching ESL to adults in Switzerland is difficult, for reasons already explained (although it is by no means impossible). The market is indeed flooded with native English speakers who have exactly the same thought as you do ("I want to work in Switzerland, and I know how to speak English...hey!"), but there is also a rather high turnover for teachers, so there is often an opportunity if you look hard enough. And whoever said that you can't make enough money to live on from teaching at Migros is full of **it, because you can. However, you may have to work at more than one Migros klubschule or other schools. Fortunately, there are a thousand schools to apply to, as well.
The downside, of course, is that you have to have a visa (unless you're a citizen). You can't expect the schools to supply you with a work visa, due to the aforementioned flooded market. It's basically a requirement. Also, the CELTA is pretty much standard. And don't worry about how much grammar you know before you begin the CELTA training--the test is really just to prove that you are willing to put in the tremendous amount of research that is required to successfully pass the course. Do your homework (most of which is readily available in online resources) and work hard, and passing the course is a piece of cake. And it really is a wonderful course. I had never taught before, and was terrified of public speaking, and I left the course feeling confident and ready to teach.
And you asked how much money to expect. As a new teacher, you can expect around CHF 50 per hour. Some schools may have you go through a "training period" wherein they pay you significantly less for a specified period of time, but whether or not it's worth it to you is something only you decide. If you decide to continue teaching for many years, some classes can offer a teacher up to CHF 130 or 150 per hour, but these tend to be very specific classes, like English for Lawyers, Medical English, Financial English, etc., which require highly specialized teaching knowledge. In other words, you can make a fairly decent living as an English teacher in Switzerland if you really work hard at it.
As for finding that dream job, there are a lot of resources. The first one that comes to mind is the ETAS website ( www.e-tas.ch ), which stands for English Teachers Association of Switzerland, the Migros klubschule website, and of course local Swiss newspapers. You may also find a connection during your CELTA. I actually interviewed for my current job here while finishing my CELTA in the States, due to some fortunate timing. But keep in mind, some schools have a better reputation than others in terms of how they treat teachers. PM me and I can give you the skinny on some of them.
Now, a word about timing...summer is a bad time to come looking for a job here. Most people are away on holiday, and not terribly interested in spending their time in stuffy, un-air-conditioned classrooms during the best time of the year. But if you take the CELTA this summer, which takes a month anyway, you'll be ready to apply in August for the positions that open up in September. As long as you have a work permit and the CELTA, chances are good that you can at least find SOMETHING.
Anyway, feel free to PM me if you want any more advice. I'm still new to the game, and don't know all the ins-and-outs, but I'm happy to share what I know.