Originally Posted by Ale
If you have'nt figured it out yet, first tighten up the two rear ones first, but not so tight that you can't rotate the bars back. Adjust to where you want them and then tighten the front two. It is a clamp type fit and you tighten the front two the rear two will clamp right down.
Sorry to say this, but:
Don't do it this way! You will way over-torque the smaller rear bolts!
You have to do one more step before:
1) Hand-tighten the front bolts (the bigger ones in the standard setting) so that the clamps are flush where the bigger bolts are (usually the front) - no gaps.
2) Tighten / torque the rear bolts now, there will be a small gap between the upper and lower part of the clamp at the rear bolts.
3) You can still rotate the handle bar with the risers to the position you like. It's just a little harder.
torque the front bolts to the correct torque. As they were flush before, you are not "pulling" on the rear while doing so.