Replace the rear shock, the OE were crap when new many didn't last more than 8k, there's load to choose from to match your budget all will be better than OE. The front is also a little soft set of up rated springs, if the budget allows get the dampener/shim stack sorted, fit a Quill Evo and a K&N couple hp more top end but it really cleans up the low to mid range.
If your's is a box eye fit HID's, don't bother with the headlight mod it's a waste of time compered to the HID conversion. Just remember you've got to convert back to standard at MOT time, some will let the HID go others wont, it's easy to convert back and forth. Or fit the later twin H4 firing, you need the bracket as well and you'll have to do a bit of modding but it's worth it, go HID with that and it's better than your car!!!
That's about it, the Fazer is one of those rare bikes where they're pretty much right out of the show room, in my opinion it's the best bike Yam have ever made and probably the best all round bike ever made.