Dan's thoughtful post on the wandering poles reminds me of one of my pet
peeves...the use of declination values over five years old. A student once
showed me the declination map that came with her new compass that was 15 years
out of date. Also, unthinkingly, using the value printed on a topo sheet dated
1957.
 
Aside from using a non-magnetic compass, you can easily find the local
declination that includes local variations and anomilies by taking a few
minutes to take a number of bearings and comparing the difference on your topo
sheet. The very latest data that you can get.
 
Best,
 
Gene Prince