You would be amazed at how many times mechanic glitches can be fixed by cleaning the machine, rethreading it, or changing the needle. I have covered the cleanliness part already. Rethreading is another useful maintenance operation to apply. If you can't seem to get the tension right, if the thread keeps jamming or breaking, if anything feels wonky, try rethreading everything (spool and bobbin). That will often solve your problem. As for needles, be sure to use the proper one for each project. Universal needles are good in many situations but they aren't the universal best choice. They won't work as well on very thin or thick fabrics than thinner/thicker needles will. Jeans for example may be your everyday wear, but they require more than your everyday needle! Needles also become blunt or bent fairly quickly. This can lead to thread jams or, worse, the needle crashing into the needle plate instead of going through the hole (and consequently breaking). Change it regularly for better, safer stitching.