I've always looked at it like the uppers keep your diaper from falling down off your hips and around your ankles, the lower tapes seal around your legs and hold the leak guards in the creases to prevent leaks. You might just have one leg wider than the other? I usually go for symmetry when taping my diapers. Sometimes the pattern isn't squared up with the physical design of the diaper though, so you can't always go by that. Some diapers have indicators like number or letter patches etc for tape placement and those are usually reliable, but not all diapers have their patterns in a consistent location.
I personally try to spot off the position of the leak guards as they run up the front. On most large diapers, the top tape ends get stuck down at some spot near or overlapping the start or the inside end of the leak guard, though it varies greatly between different diaper designs. Then I place the lowers relative to the uppers, usually down and out about 3/4", and facing down at about a 45 degree angle.
The exact place you put the tapes is pretty open to debate and trial and error though. Once you find a good fit, when its time to change, cut the sides off and lay down the diaper and take a good look at where the tapes are on both sides. Remember this for next time. I've gotten to where I know exactly where my tapes go on most of my diapers, and I can tape them before pulling them up. I get a perfect fit every time, and it takes a LOT less time to diaper up. No dealing with needing someplace to lay down, a wall to lean against, etc. Just can't do that without removing my shoes/pants if I need to change in the field.
Also on the subject of flooding, make sure you leave a channel down the middle of your diaper in the crotch for liquids to flow. If your padding is hugging you skin-tight in the crotch, you're very likely to leak when laying on your back - it'll just back up and flood forward, running out the tops of your legs or in the middle of your crotch. The DC Amore are very fast absorbers, they take floods better than any other diaper I know of.