Probably the most important thing is to actualy have a good tune to 'drop'. If you're dropping a bomb it's obviously going to be a lot heavier than if you're building up to some half arsed fire-cracker, where no amount of buildup work will make it sound powerful.
Besides that obvious gem, think of you're drop as being your 'fullpower' mode, where your tune is well produced, full spectrum (low freq - thru high freq), well mixed (therefore loud as possible). Basically, quality.
Now in the build up, subtly reduce some of the frequencies (eg cut low end, or have no sub low end before the drop?) or low pass/high pass some of the elements leading to the drop.
If you do it quite subtly, and give the ear just enough time to adjust to the weakened sound, then the drop come across more punchy/weighty
Or you could use fx, as in have a reverb that slightly reduces the power of/muddies your bass, then cut it on the drop. etc etc
Just some thoughts about the sonic aspects as well as the structural elements of the build up.