Marie, you have to tell us what you're sewing? I have my mom's Singer sewing machine from the 50's and it still works fantastic (most of my errors are "operator errors"). The setting for this machine for straight sewing is "A" and "K." Hope that helps.

Do you have the manual? If not, try troubleshooting by doing searches on-line. Like if you notice the thread is bunching up top, do a search for that and see what is causing it. It helps to have a scrap piece of fabric to mess around with until you get the dials where they need to be.

It's kind of hard to tell you where the dials need to be because it depends on the machine, the type of thread, the type of fabric you are using, etc.