I believe there is already a thread about this, if so, CS staff will merge this post into it.

Watch my preflight sequence video, it covers the proper initial preflight settings for the 757.

http://www.youtube.com/watch?v=6X0QjqGHkYk

This also includes alignment of the IRS.

When you first turn it to Align or NAV, the ALIGN indicators should light up.  If you're on DC power and draining the battery, the ON DC indicators will also light up.

Either way, you must be stopped, parked, on the ground, for alignment to occur.