Cleaning a carburetor is a fairly easy job, but it can be intimi****** the first time you have a go at it. I would recommend buying the rebuild kit. Once you've gone through the hassle of removing the carb, disassembling it and cleaning it you might as well make sure all your gaskets and seals are new so as to maximize the amount of time you have until the carb needs overhauling again.
What you clean it with depends on whether or not there are any plastic pieces that won't be easily removed from the carb itself, such as a fuel inlet. If the carb has no plastic pieces, use plain old automotive carb cleaner. If it does have plastic pieces I use iso-alcohol.
My advice is to have your digital camera handy while you do the job and take multiple pics at each step. That way when you're reassembling and remounting the carburetor you have photographic evidence of the proper setup. Taking pics is a massive headache-saver.
As far as preventing carb issues in the future, there are a few things you can do. First, if pure gas (no ethanol) is available in your area you can use it in your engine. Second, make sure you prep your engine properly in the off-season, either by draining off the fuel or treating it with stabilizer.