One of the greatest fears amongst those new to overlocking or serging is changing the threads in the machine. I would only ever use a fabric that matched the cottons that were already in my machine. It's really important to get it right or you will find yourself with skipped stitches, broken threads or horrible tension.
If your machine is like mine (12 years old!) and doesn't have a fancy self threading function, that's OK, here's some tips to help make it a breeze.
Take a note of the settings on your tension dials before setting them all to '0'.
Overlockers and sergers need to be threaded in the correct order. Either refer to your instructions manual or there may even be a threading chart outlining the order placed on the machine such as mine does.
Cut your thread. It should be done in between the Thread guide and thread guide plate. The looper threads use twice as much thread as the needle threads so place your fullest spools on these two.
Something I learnt only recently while sewing with my grandmother (she was an industrial sewer), was the importance of knotting the threads. She picked up that I tied a knot like I did a shoelace. This would often come undone while pulling it through and you can almost bet that it would be one of the loopers!
Tie a knot with the threads 2 ply - I do hope the image makes up for my inability to explain this properly!
After the threads are all through, cradle each thread through the tension dial to ensure it is engaged.
Then reset your original orginal tension settings and you are good to go.