i've got this stretchy t-shirt fabric. every time i try to sew it, it pulls in the machine, which results in a stretched out, bunchy look. how can i sew a simple straight line into this type of fabric w/o having it stretch as it's being sewn?
Are you using a ball-point needle? You need one for knits, it slips between the stitches instead of poking the fabric... Also try using a longer stitch length, with a narrow zig zag.
definitely make sure you are using the right kind of needle. Make sure not to pull the fabric under the presser foot, let the machine do all the work, only use your hands to guide it. You might want to try and sew over a piece of masking tape, then pull the tape off afterwards. That doesn't work in every application, but it can help.
If your machine has a triple stretch stitch, use that. Also needles are very important, use a needle designed for stretchy fabrics. Also if you don't have a Triple Stretch stitch, you'll have to zig zag it.