[Not legal advice] General tip - always remember everything is negotiable. Just because someone hands you a form contract doesn't mean you have to sign it as is. IP's tricky, but basically you own what you author until you assign the rights (unless it's a "work for hire", which generally doesn't apply, see the Wiki). The company you're freelancing for likely expects that you'd be signing over all the rights to the work product to them -- they're paying for it, after all. If you expect otherwise, then you should document that you're only providing them with an indefinite license to use (they'll probably want the right to modify and own all mods).