Why don't you look through the Games resources. You'll find loads of fla files for free download. Open them and see how they were made. That's where I'd start.
there are a bunch of things you could start with. something that doesn't have much action in it would probably be easiest, perhaps a guessing game of somekind (eg rock, paper, scissors) or maybe a magic 8 ball type thing.
you could also investigate tile based games, the concepts used in these can be applied to many genres of game, commonly things like pacman or grid based puzzle games (such as http://www.moddular.org/experiments/blockpuzzle.html though this is javascript not flash ) there are many excellent tutorials out there on the subject, in particular you should check this one out http://www.tonypa.pri.ee/tbw/index.html
hmm the first game i ever made was a first person adventure type thing. where you click on things and it tells you info about it =) it was pretty simple
i love flashbax ... i asked u for a counter once, long ago...
is ping-pong a good game to start? i made one, but it can not hit under angles it's somewhere in flash newbies forum ... if anyone think that can help .. thanx ...