I use a Q-Tip and some machine oil (you can get this at Wal-Mart, It is Singer oil, but works for all machines). Use the q-tip with oil on the tip and work all around the feed dogs and the bobbin housing and all the working parts around it. This will help keep it clean. I also use a stiff paint brush and get all the big pieces of lint out. Don't blow on the feed dogs and the bobbin housing, that only drives all of the lint and other debries back into the back part of the machine and can cause you all sorts of problems later. After all of that is done then put 2 small drops of oil on the inner part of the bobbin housing, where the bobbin sets, if you can take that part of the housing out of your machine, I can as I have a Berninia. Then run the machine for about a min and it should be oiled and back to purring like a kitten. I would probably do this after every new project like when you change your needle.
An after thought, before you start a new project after oiling and cleaning your machine, make sure you sew on a old piece of material, just incase you have any oil anywhere you didn't know about and it won't ruin your new pretty material.
Jennifer :)