I think if your cuts turn out right, you're doing it right. All else is just a matter of technique.
I usually use TWO rulers to cut fabric if I'm cutting folded yardage. 8x24 laying on the fabric (usually) and my 6x24 is what I actually measure with. So I line up the 6x24's measure line with the edge of the fabric (say it's a 4-1/2 inch cut, so I line up the 4-1/2 line with the edge of fabric) and butt my two rulers together. This gives me a long line along the bottom folded edge so I can make sure I'm nice and square with the fabric. (if not, I square up, then re-align). Then I hold down the 8" ruler, slide the 6x24 over a bit so I get cutting space, and cut my strip.
Having the two rulers in action really helps me stay square when doing long cuts. I don't usually bother with that for small cuts.