I'm in the process of a new build myself. The biggest lessons I've learned from my previous builds are:
1) Begin with the end in mind. Think about what you want to do with your tank. Get an actual plan for what kind of livestock you want, what kind of equipment, etc. Then build to that.
2) Cheap stuff is expensive. You may not have to reach for top-dollar equipment, but the mainstays that all the other hobbyists swear by are the ones you should look at. Stay away from pumps, lights, heaters, etc. that won't be good enough to do what you need them to do. I went through a bunch of cheap equipment and still ended up buying higher end stuff...point learned is that every dollar spent trying to avoid buying the hobby standard equipment was money flushed down the drain.
3) Get a controller. :D A controller isn't a necessity...but I'll never have another tank without one. :D
4) Go SLOW. This isn't a race, so plan to take everything nice and slow. Get your tank fixed up into something you'll be proud of.
5) QT everything. I lost all my fish (well, 18 out of 20) to what I believe was marine velvet. All of my livestock was fine until I added the very last fish (a wrasse) that I had planned to add...then watched my fish die over the next 2 weeks. I felt horrible. I also had to deal with a bought of zoa-eating nudis as well as monti-eating nudis...now I QT everything that goes in the DT.
Hope those points are helpful...they may be more philosophical than what you're looking for. :D