Just like every other drum, you are going to want to make sure that all of the lugs are under the same relative tension. The best way to do this is to gently tap around and between each lug making sure that all of the taps sound the same and create the same tone. The snare has some specialties to it though:
The bottom skin, most of the time, will want to be tuned higher than the top skin. This creates punchy overtones instead of muddy overtones. when people think of muddiness, they tend to think around the 250-400 Hz range. The primary tone (the main frequency) that snares tend to create is about 200-220 Hz. tuning the bottom skin higher, a perfect interval higher (4th, 5th, octave), tends to keep those “muddy” overtones away, and gives the snare more punch.
One of the other things that is interesting about snares is that many more heavy rock drummers will detune one lug. Though I did not do this for the book, it is something of interest. The idea here is to give the skin somewhere built in to do the same thing as rings and moon gel — trap the tones in some place under less tension.