Summarize the following:
One of the things that can make the difference between true north and magnetic north so difficult for navigators is that the effect on compasses can change over time. This phenomenon is called declination as the earth's magnetic field fluctuates, the number of degrees by which a compass will be "off" from true north will shift accordingly. Thus, to accurately adjust your compass to account for this effect, you'll need a recent declination value for your location. Luckily, the National Geophysical Data Center (NGDC) keeps up-to date records of global declination values. At the NGDC website, you can enter your current location to receive the most recent declination value available for your area. Some physical maps will also include declination values for the area displayed in the map. Topographical maps are the most likely to include this information, though it can be in other types of maps as well. If you're considering navigating by map and compass, consider checking your map's legend to see whether the map contains accurate declination data. Note, of course, that declination changes over time, so old maps can quickly become out of date. For the most accurate values, use the most recently-published map available. Once you know how "off" your compass is from true north, it's not hard to adjust for this discrepancy. Begin by finding magnetic north. Hold your compass flat and level in front of you. If your compass has a travel arrow (usually a skinny red arrow on the flat lower portion of the compass, point this forward. Watch the motion of the compass needle. When the needle stops moving, note the direction the needle points. This will be the north-south axis. Most modern compasses have a needle that is half red and half white. In this case, the red end of the needle is the north-pointing end. If you're navigating by compass, typically, at this point, you would adjust the compass's bezel to that the direction you're intending to travel is directly in front of you, aligned with the travel arrow. In this case, since we want to find north, we'll turn the bezel so that the "N" (and the wide arrow beneath it) is directly in front of us. Note that this magnetic north, not true north we still need to adjust for declination. Turn your body until the compass's needle is lined up with the orienting arrow on the bezel (and, thus, the travel arrow as well). You are now facing toward magnetic north. To find true north, turn the bezel the same magnitude and direction as your declination value. Most compasses will have degree markers on the bezel to help you do this. Next, line up your needle and your orienting arrow by turning your body again. You should now be facing true north! For example, let's say that we originally obtained a declination value of 14o E for the area we're in. If we're facing towards magnetic north, we would turn our bezel 14o to the east (clockwise, in this case). Then, we would turn to the left (which is west) to line up the needle with the orienting arrow, leaving us facing at true north (14o west of magnetic north).

Summary:
Find your local declination from the NGDC. Alternatively, find your declination from a map. Find magnetic north with your compass. Turn the orienting arrow so it points ahead of you. Adjust for declination.