First, you'll want to have the resonator on the banjo. You also need to make sure the strings are tuned to standard pitch and that the intonation is set correctly (check the section on bridge placement if you're not sure how to do this). The note you're tuning it to is based on the resonant frequency of the entire tone chamber, not just the head itself. This is a bit confusing, but if you try to tune the head itself to a G#, for example, without the resonator on, it will probably be way too tight. You'll also want to dampen the stings to eliminate vibrations we don't want to hear.

Tap on the head close to the stretcher band. The note will change closer to the center and be more difficult to hear clearly. Find a spot far enough away from the stretcher band so that the note is loud enough to hear clearly but not too far in to make is more difficult to hear its pitch. I usually start about 3/4 of an inch or so in. I use my right index finger with a finger pick on it to do the tapping. When I say “tap” I mean strike the head crisply and quickly. Pick up your finger immediately so you don't muffle the note.

On some banjos the note will be pretty easy to hear and on others you may need to experiment until you can hear the correct note rather than overtones from other parts of the banjo or the strings. If you really can't hear a clear tone stop and try again later.

When you think you're hearing the right tone check the frequency by finding the note on the 1st string that is closest to the tapped note. You may want to try to hum the note after hitting it so you can remember the pitch better. Sometimes hitting the head a bit harder or softer will work best. Or try scratching the head with a finger pick. You should hear a fairly clear though not loud note. Keep trying until you can do this. If you really can't hear a clear tone stop and try again later. I have days when I can do this pretty easily and other days when I just can't hear it at all (40+ years of playing the darn thing might be somewhat to blame).

The note you're listening for should be close to the sound of the 1 st string between the 3rd and 7th frets. The range most people shoot for is between G at the 5th fret and A at the 7th fret. You may need to compare the tapped note to the fretted note several times until you start to hear how the both sound together. Check if the head is tightened evenly. Go around the head tapping by each bracket to see if you hear the same note each time. The odds are that you will hear some variation. Loosen the bracket a little bit if the tap there is high and tighten it if the note is low. You shouldn't need to turn the wrench more that an 1/8 of a turn of so. Getting the head evenly tightened really improves the overall sound no matter what note it's tuned to. I also go back every day of so after putting on a head to check this and every month of so after it's settled in. No matter what pitch a head is tuned to it sounds better if it's evenly tightened.

There's another subject that comes up frequently in connection with tuning the head. This involves tuning the tone chamber by modifying the depth of the resonator. Some banjo makers design them with resonators that are deeper or shallower than others as well as having the inside of the back curved or straight. My feeling is that a quality banjo has a particular sound that the maker intended so if you don't like it you shouldn't have bought it. I don't think too many of the lucky owners of original Gibson flatheads from the late 30's are playing with their resonators to get more sound out of them.

Having said this, I did experiment with this in the 70's after talking to Eddie Adcock who did it for years. I used washers to go between the brackets on the resonator for the screws and the bottom of the flange. If you tape them to the bracket and poke a hole for the screw to go through the tape they won't fall off every time you take the resonator off. You'll hear a noticeable change. Another way to make adjust the chamber size is to look at the brackets attached to the rim that hold up the resonator. These can get bent down over time shrinking the tone chamber a bit. You can try bending them upward closer to the bottom of the flange. This can make enough of a difference to hear. Jack Hatfield sells something called Raejusters that work very well and can be easily adjusted if you want to seriously experiment with this.

In general the bigger the tone chamber the louder the volume (should be no surprise). At some point you start losing tone at the expense of this volume and the banjo sounds loud but thin. You want to find the point where the sound starts to open up giving you more volume while keeping the lower notes sounding full. You shouldn't have to change the resonator height very much to start hearing a difference. Just as I recommended that you keep the tension on the head even, you'll also want to make any changes in the depth of the resonator even as well. You'll be able to hear a difference if you do.

Given the volume of a good banjo properly setup and the quality of microphone and sound equipment today banjo volume is rarely an issue. Not that banjo volume is a bad thing of course. The ideal is to get the right tone as well as good volume. Try this for yourself if you think it might improve your sound.