I have students come in for class all the time with a machine that is going "chug, chug, chug". Our machines should sound smooth, quiet and happy. A happy machine makes for an enjoyable sewing session. So how do I do proper "maintenance on a sewing machine"?
First, take out the bobbin and the bobbin housing--if yours is supposed to come out! Unthread your machine. Now check in your "goodie" box that comes with your machine. There should be a little brush in there. If you have misplaced this brush, an unused makeup brush will do the trick (my brush of choice). Some machines come with a container of sewing machine oil. If there is no oil, check your manual. Some machines do not require any oil.
Remove the throat plate of your machine (the flat silver piece with markings under the presser foot). Now, carefully, sweep all of the dust and lint out of the machine. Make sure to sweep around all of the parts. Now sweep the area over the presser foot, where the shaft comes out of the machine.
Oil your machine carefully using the guide and directions in your manual. Some machines have several places to oil. Mine needs only one drop. Use only sewing machine oil!!!
Replace your throat plate and bobbin housing. Dust off the entire machine. Rethread the machine and test drive with a piece of scrap fabric. You should have a very happy sounding machine.