There are a number of methods I use.  One is a product called Dust Away. It is flammable gas in a can and has a long plastic tube which is inserted into the noozle.  Its great for getting into areas of your sewing machine that you cant get into, like under the bobbin.  I have heard people say not to use it.  However I have used it for over ten years and my machines are find.  But I do not have computerized machines, so check with the manufacturer first.

I am going to give you the website and you can have a look at where your nearest distributor is  www.helmar.com.au and go to  Products then at the bottom is "Where to get our products".  I buy mine at a computer shop, because its used to get into nooks and crannies in computers

I also use ear buds to clean away thick fluff in my bobbin casing.  I would clean this out a minimum of once a month, probably more regularly than that sometimes depending on my work load.

When I am vacuuming the house I give my over locker a quick work over with the vacuum.  Make sure to hold on to the threads.  When cleaning your sewing machine, always be away of threads coming out of their regular threaded positions.

Happy altering
Judith Turner