I'm not sure what to tell you.  If you want to start learning about what we do here, the welcome message at the top of this page has some useful links.  I tried to give you the nutshell version above.  If you're looking for some list of exact rules, you won't find it here.  Yes, people do sometimes write about themselves on their user pages.  When it crosses the line into promotional material, this is when most editors will start objecting to it.  I don't think you're likely to be flamed, banned, squished, or whatever, if you exercise a bit of common sense.  When in doubt about what to do or not do, just ask yourself "Does doing this make Wikipedia better?"  It's usually as simple as that.