As noted, you do need to account for declination on the quad maps that are generally used for AR. Don't necessarily trust the declination on the map. The magnetic pole moves over time and the quad maps can be 30 or 40 years old.
You can calculate local declination values here:
http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp
Maybe you aren't suggesting this, but for the beginners out there: You shouldn't try to navigate solely by compass bearing. Even the best compasses are only accurate to within about 2-3 degrees. Walking a bearing on flat open ground is hard enough, but in the forest with uneven terrain....
Definitely use the compass for directional guidance, but you need to learn to translate map features to actual terrain. Even if you are walking a bearing and you don't follow features, you'll quickly lose contact with the map.
Best way to develop this skill is to go to orienteering meets
Shameless plug: St. Louis O Club is having a meet next weekend, including a 16K course with a 6 hour time limit.
