Flying Directly Toward an NDB
To fly directly to an NDB, first turn the airplane so that the needle is pointing straight ahead. The airplane is now pointing directly at the NDB. Just like with VOR navigation, the airplane will soon drift off course without proper crosswind correction. The process is the same, the pilot only needs to understand the different display of information.
Maintain your heading, and observe the movement of the needle. If the needle moves right or left, you will have to turn right or left to stop the airplane from drifting off course with the wind. For example, let's say the needle moves to the right five degrees. We must turn right to correct for this. So, we turn 15 degrees to the right. Since the ADF needle always points directly at the station, it is now pointing 10 degrees to the left.
The tricky part is to realize that we want the needle to show an angle equal to our wind correction. Since we turned 15 degrees to the right, the needle should show 15 degrees to the left of our nose. At the moment, it shows 10 degrees left. Maintain this heading and watch the needle for a few moments.
Let's say the needle continues to move to the right, and it now shows 5 degrees left of course. This is an indication that we're still drifting. A greater course correction is required. We turn another 15 degrees right. Our total wind correction is now 30 degrees to the right. So, we want the ADF needle to show 30 degrees to the left. It shows 20 degrees left at the moment. Maintain heading and wait.
After a few moments, the needle begins to move to the left. When it shows 30 degrees to the left, we're back on our original bearing to the station. At this point, we know that 30 degrees is too much wind correction, and 15 is too little. We elect to turn 10 degrees back to the left, which leaves us with a 20 degrees to the right wind correction. The ADF needle points 20 degrees left of course, and that's where we want it. Maintain heading and wait.
Continue bracketing until you find a heading where the ADF needle does not move right or left, and make corrections as necessary.
Flying Directly Away From an NDB
First, turn the airplane until the tail of the ADF needle is pointing directly ahead. The airplane is now pointing directly away from the station, but drifting with the wind. Search for the wind correction angle by maintaining different headings and bracketing.
Movable Card ADF
Some aircraft are equipped with a movable card ADF, in which the pilot can rotate the compass card in the ADF. The pilot could align the card with the aircraft's heading to ease visualization of the information depicted on the ADF. With the heading dialed into the ADF, the instrument would indicate magnetic bearing instead of relative bearing.
Remote Magnetic Indicator (RMI)
An RMI is a navigation instrument that uses a gyroscope to move the card of an ADF for you. In addition to an ADF needle, an RMI often also has a VOR needle.
Like a movable card ADF, an RMI indicates magnetic bearing. You just don't have to set move the compass card every time you change your heading. Navigation using a movable card ADF or RMI is the same as with a fixed card ADF. It is just easier to visualize the information presented on the instrument. When a VOR needle is displayed on an RMI, you can navigation in reference to a VOR just as you would an NDB.
Reference: AIM 1-1: Navigational Aids
Reference: AIM 1-2: Area Navigation
Reference: Instrument Flying Handbook Chapter 9: Navigation