Tension

Experts are always saying you should never ever mess with the tension of your machine if it's all out of wack. They don't, however, tell you how to fix it without touching that sacred tension knob. The majority of the time your needle is the culprit of the wacky stitches. All you need to do is put a new needle in and that usually will fix the problem. Still having issues? Experts might haunt me for saying this, but sometimes your bobbin case is the issue. If you look on the case, you'll find a little screw, tightening or loosening that screw the slightest bit can make a world of difference. If you're still having issues, it's ok, you can touch that tension knob (especially if it's your on personal machine; if not...it'd be best for your health to just leave it be.). I honestly, don't know which way to turn the knob to loosen or tighten the thread (having obeyed the no touchy commandment), so if anyone knows please share the knowledge! Otherwise, just fiddle with it until the tension is back to normal.

There is also a way to tell whether or not you need to bother with the bobbin case. If the wonkiness is happening on the underside of the garment, then it's usually the top thread that is either too loose/tight. If it's on the upperside (the side you see while sewing), then it's the bobbin thread. I'll explain this more later with pictures (I'm getting myself confused trying to picture this stuff in my head...sad).