Certainly you want to practice the right things right! It's hard enough learning something once, let along having to unlearn it, and than learn it correctly again.

Having the sound of the scale embedded in your brain is very helpful, and you can get this by practicing the scale repeatedly while getting it into your muscle memory. The major scale is a good one to start with since even a non musical person will recognize it. Then you'll be able to do the major scale anywhere on the neck starting on any fret on any string. Maybe you won't be able to hit it straight off, but you'll be able to figure it out quickly because you'll know if you hit a bum note - you know how it sounds!

Committing the formula "wwhwwwh" to memory helps too. This is the formula for the major scale starting with any note and is also what the modes are derived from (when you get there).

What helped me with this was putting down my guitar and applying the formula "wwhwwwh" on paper, from any note figuring out the other notes in the scale, and drawing the patterns out for the fretboard. Essentially, you can derive the 5 scale patterns for yourself. This way they mean something to you and aren't just a magic pattern.

You are correct that it is worthwhile to revisit lessons especially where you may have not absorbed everything the first time. You learn more and going back, you have a better context to understand it with. Happens to me all of the time...and will continue to do so I'm sure.