Along with what Jeff said above... I change my main (spin-on) fuel filter at 25kmi intervals. I think the official factory specified interval is 30kmi. (?)

The little plastic one, well, if you can see inside it, you probably don't need to change it unless it's got crud in there. But I usually end up changing it at 25kmi as well, unless it looks remarkably clean. If you can't see inside (some are opaque instead of clear), change it at the same time as the big spin-on filter.