Another thing you can do is to put two different colors of thread in the machine, quite different colors. Put for example red on top and bright blue on the bottom. The reason for doing this is so that any misaligned tension will show up right away. If the bottom thread is pulled through and visible on the top, either your top tension is too tight or your bottom tension is too loose, or both. If your red is visible on the back side, then either your bottom tension is too tight, or your top tension is too loose, or both.
I have a Janome and this is how I check my tension. And yes, I do adjust the bottom tension. They used to teach it to us eons ago when I was in Home Economics (about age 14 on), and now they don't want you to touch the bottom tension, which is rubbish. If tension is the only problem you see, that's fairly minor, and can be worked out with patience and slow changes in each top and bottom tension.