To become a wedding planner you don't necessary need any specific qualifications. However if you did have qualifications, it would be seen as an advantage. there are many colleges that provide courses in wedding planning, which may be of interest of you. Of course this depends on your age, but I suggest you take a degree in something you are interested in at University (which will allow you to enter any field of work) and then perhaps take a year out to study at a wedding planning college. Maybe look around on-line to see if there are any courses that appeal to you. I don't know if you are in the UK or not but this is great: http://www.weddingplanningschooluk.com/ if your in the US then I'm sure there are similar courses there.
When it comes to salary it varies, and mostly depends on your years of experience, so when first starting out in the business you can expect to earn from £16,000 to £25,000 a year. An established planner could make £30,000 - £70,000 and a high end planner with an impeccable reputation could make £300,000. To become and 'established planner' you will need to get contacts, which can be built up through a wedding planning college (as previously mentioned.)
Probably the best way to break into this area of work is to work for a company at first, allowing you to build up your contacts, and get a real feel for the job, maybe after a couple of years you could start your own business, having built up the experience you need.
There are many different sides to a wedding planner, have you also considered being a wedding stylist? A wedding planner can be hired right from the engagement, and can deal with the engagement party, and all other events up to and including the wedding. A wedding planner could also be hired just for the day of the wedding, when the bride just needs someone to overlook the running of the wedding.
If your really interested in this kind of work, then I suggest you look around on-line, there is lots of websites that may interest you, I have listed some below:
http://www.myjobsearch.com/careers/wedding-planner.html
http://www.inst.org/wedding-planner-courses/become.htm
http://www.weddingplanningacademy.co.uk/
Good Luck!