I'm in the same boat as you, very new to the hobby. Here's some sage advice I received from some more experienced reefers.
Add a pond liner at the bottom of the stand to catch some of the spill. Make sure that the water can't rise high enough to engulf your return pump, or the collected water will kill it.
Plan out the plumbing in advance with a manifold off of your main discharge. Don't toss 6 submersable pumps into your sump and expect that to work out. Seriously, I had planned on all pump-driven equipment until I heard from smarter people.
Buy as much as you can used. People jump out of this hobby like a burning building, and you can catch some really good deals during the summer when everyone's busy outside playing.
Plan for an electric-friendly system from the get-go. Keep as much equipment as you can out of the water (external pumps). Run fans over the sump area. That way you won't need a chiller as much. Run good reflectors on your halides so they don't have to stay on as long. etc.
Position your tank at least a few inches (if not farther) from the wall so that you can reach behind it.
Buy appropriately sized equipment that you need now rather than something that might barely work that you'll have to replace ("upgrade") later.
With any tank over 200 gallons, have some kind of ventilation plan for the excess heat/humidity.