There are 2 setting concerning your highbacks that will be important to you. First and most important is your forward lean. This is the vertical angle that your highback is set at.
Increased forward lean allows you to increase power transfer to your heel edge to make heelside more responsive while being able to keep your body stacked vertically over your board (less need to lean back in your heelside turns which is a good thing). It also helps the rider for toeside and all around riding because it helps position the lower legs into the ideal athletic stance with knees flexed. Higher forward lean settings are preferred for free ride oriented riders and low forward lean settings are generally preferred for freestyle oriented riders who need and desire greater free range of movement.
The second setting is called highback rotation and this is the lateral angle of the highback in relation to the base plate. This is really a personal preference issue and does not have a huge impact on board performance really. Most bindings have 2 to 4 possible settings whereby you can either align the highback with the base plate or rotate it to align in more with the heel edge of the board.
When aligned with the base plate, this also keeps the highback more aligned with the calf of your leg which is what I tend to prefer in my own riding. When you align your highbacks more in line with the heel edge, there is some increases leverage when you execute heelside turns. Personally, I have found this to be pretty negligible. Some riders that are having some trouble with their heelside, do find that highback rotation solves their issue. I would advise setting them aligned with base plate and ride a bit, then try rotating them to see if you can feel a difference. Some do claim to notice less knee pain one way or the other; depends on the rider.
thanks man, im gna try them more parallel to the edge and see...i had my front one adjusted completly parallel but when i folded the highback down it wouldnt go all the way do cause such an angle, so i moved the inside side of highback back a notch