You may know more than you think. I suggest printing and filling out a few charts: family group, pedigree, etc. You can find them for free at the library or online (here, for example.) The point is to get organized and figure out what you really know.

After that, I'm afraid it's down to detective work: Posting queries in online forums related to the surnames you're researching, scrolling through census records (free at the library or by subscription online), and so forth.

But the first step is to "interview" yourself, and document what you know.