155 gallon tank and a newbie. . . . .

Congrats! That tank will be a beauty when setup!

In terms of stocking--there are several kinds of community tanks you could go with. One option would be to start out with reef-compatible fish, so you can upgrade lighting and go reef if you want. Other option is to just get the fish you like and can care for, with no intention of going reef in this tank. For example, triggers are not reef safe, but can be mixed with a variety of fish, especially in this size tank.

If you plan on going to a reef down the line, you'll need to upgrade lighting--at least another set of 96 watts. You may want to look into a deep sand bed, and how it functions in the tank to aid filtration.

The best and easiest way to cycle the tank is to get the substrate in there (decide if you want a dsb now--much easier to put it in at the beginning, than to remove the crushed coral later!), add the base rocks (not live rock, just the platform for live rock), add the water. Throw in 10 cocktail shrimp from the deli, and begin testing the water for ammonia, then nitrites, then nitrates (did you mention a test kit?).

I like the Master's test kits, but there are a bunch of good ones available. You want to test for ammonia, nitrites, nitrates, pH, calcium, phosphates. While cycling, ammonia and nitrites will be the big ones to watch. Once the tank stabilizes and matures (6+ months, depending on), nitrates and other water parameters will be the top things to watch. You cna get either a kit, or buy them separately. I like the kits becuase it's easy to organize and use when everything is all in one spot. I highly recommend getting a small notebook, and tracking your testing results as well. Makes it easier to see how the tank is progressing if it's all written down and dated.

Okay, then you'll just need to make sure everything is reef safe, and plan to upgrade to metal hallide, power compacts, or VHO lights eventually. With that size tank, MH are your best bet, since they will provide better depth penetration.

For sand depth, 3-6 inches, leaning towards the 6. You can use any small grained sand (ie, blasting sand, play sand, from any big box store). Southdown Play sand is coveted, but not necessary. Once the tank has cycled, you can purchase a sand bed activator kit (GARFS, fishexpress--there are several places that sell these) to get some of the critters that will maintain the sand bed for you, in addition to a clean up crew of hermits, shrimp, smaller crabs, serpent stars, etc.