999 model..??..Vaseline. Replace the fuel filter...check the accordion fuel lines that connect to the fuel filter. Make sure they are not cracked. The clamps Ducati uses in there are Oetiker clamps, I'm not sure if they are reusable. You can change over to a standard hose clamp, but make sure it is a hose clamp so it won't chaffe. If you decide to stick with the Oetiker clamps, you'll need to buy a special pair of fastening pliers.
When I changed out my filter I found that placing the tank upside down on a bed of soft towels or sheets protects the tank and puts you in a better position to get over the fuel pump and press it down evenly. Getting the O ring in is a PITA... There is a tutorial in our "Halls or Wisdom" section regarding this.
998 you can just gently screw it down one bolt at a time, alternating from side to side. Grease it with some standard stuff (bearing grease etc, it won't hurt). It's not that hard, you just need to take care that you bolt it down evenly and watch that it doesn't get pinched.