Heat: how early to set it, how to manage it.

Setting your 'heat budget,' ie heat range in tank...
IMHO, of all the things you can do to REALLY hasten cycling, this is one. Get your tank to a steady 79 degrees, with a rise and fall of as little as you can---1 degree would be good.

To do this in a way that will be useful in future, set it with everything running as it will run when there are fish/corals. This means your lights on timer, 12 hours of blues/actinics/moonlights, 8 hours of daylight---in my tank, this means the actinics are (as well as an energy source) a color correction in my otherwise nastily yellow 10000k Metal Halide lights. Their 12 hours includes the 8 when the MH is on. Those of your with LEDs may make other choices, but your lights will not give that great an energy input to the tank. [LEDS are a much better choice than MH for people in climes where heat is an issue.]

Also have all your canopy fans (if you have such), skimmer, with its pump, return pump, and if you are setting up a fuge in 20 gallons of your 30 gallon sump [if you have such] this is an excellent time to do it: I have a sand/rock/cheato fuge that is a great source of stability and free fish food: I have a mysis shrimp colony down there, along with amphipods and copepods.]

In short, run everything that contributes heat to a tank, all the bulbs, pumps, etc, and let 'er rip, full schedule.

Your first job (you need do nothing) is to let that rock and sand warm up. That takes days and days in a larger tank. Once it's the same temperature as the water, understand that that 'heat reserve' is ALWAYS going to operate slower than your water. It'll warm up and cool down with many hours of leeway, so any time you're adjusting your heater, remember to go on checking it---when the rock catches up, you may have too much or too little heat.

This makes the rockwork a lifesaving shelter for your fish in a power-out or overheat.

Your second job is to try to minimize that swing, which will happen gradually, as all the temperatures in the tank even out, and as you figure out where your heater setting should be to achieve that 79 degrees (can be a shade more but not much less.)

Here's the bonus: chemistry including biochemistry (life) runs faster when it's warm than when it's cold. This is why your fish are safer in a cooldown than in an overheat. And this is why warming up your tank actually works to speed up your cycle.

The fastest way to cool down a tank is to turn a fan on the water surface. Always remember that. One way to hold heat in a tank in a powerout in winter is to sheet 3 sides (leave one for room light to get in) in styrofoam or insulation or even a thick blanket, which retards radiation of heat from the tank.

A parting point: the heater you buy should be a very good one. Don't go cheap on heaters. Remember this is where you most directly put something electric in water with only a piece of glass and waterproofing between you and disaster, even fire. First of all, buy the best---AND be sure this is on a GFI circuit, aka one of those plugins with a button that pops out to break the circuit if there's a short. This can save your tank, save your house, and save *you*. All tank equipment should be on GFIs, and just factor that cost in with your tank. The best heater. And ground-fault-interrupts. This is important.