Depends what you are trying to clear out of your beer, loosely there are two types of "clarifying" one is particulate the other is chemical.
Particulate haze is things like trub, yeast, bits of hops... Cooling (whether fast "Crash", or slowly) both reduce the activity of yeast and the background Brownian motion of the system so stuff that is heavier tends to fall faster.
Gelatin finings used properly will improve the rate of clearing, it tends to pull electrostatically charged chunks together so they fall faster.
Chemical based haze includes Chill Haze and Glucan/Protein but unless you have really stuffed up your mash we are going to be mostly concerned with chill haze.
Chill haze is a temporary association between higher molecular weight protein and polyphenols (tannins (sort of)).
Forming haze by cooling and then waiting for the haze particles to fall to the bottom is also called Lagering or Chill Proofing.
Gelatin wont help with this type of haze, Isinglass will, as will patience, often several weeks worth. Certainly happens faster cooler, commercially Lager is cooled to just above its freezing point (~-2oC) for at least 7 days and often much longer (up to months). it is very important to either rack or filter the clear beer off the trub before it warms or that temporary association will reverse and all the Haze causing matter will go back into solution - undoing everything achieved by chilling.
If you want to get a bit more technical, the rate of sedimentation follows
Stokes Law.
Mark
