Will this be a standard 20 gallon high?
Maintenance is fairly simple once it's setup and running you will need to 10-25% water changes once a week. Depending on what coral you plan on keeping you may need to dose a two part solution 1st part Calcium 2nd part Alkalinity(stony corals), but that would be later on once your tank is more mature.
The bulk of all of your filtration will come from live rock. You could have a hang on back style filter on there just to pick up free floating particles in the water but you should change the filter floss in it at least once a week to get rid of the nitrate causing detritus.
I recommend at least 1 lb of live rock per gallon of water after that it's really up to you some people like more some like less, I prefer more open swimming room.
Lighting should be the biggest investment you make equipment wise, don't skimp. For the size tank you are talking about i would go with a 4x 24" T5-HO setup, that would allow you to keep a fairly broad range of corals. Another cool thing about T5 setups is that you can change out the bulbs to different spectrum's should you be dissatisfied with the stock bulbs. Another option would be a 150 watt metal halide. You could grow probably anything with the metal halide but you have to replace the bulb far more often than the T5 setup, and the MH puts off a lot of heat vs T5. One major plus to some people is that metal halide is a point source light(basically emanating from a super small location versus spread out throughout the entire bulb like fluorescents) you get a shimmering effect in your tank, and some people list that as their absolute favorite part about running MH.
If you keep up on your weekly water changes and find a good balance of feeding your livestock so that you aren't overfeeding and throwing your tank out of whack you shouldn't need a protein skimmer. Should you feel the need to get one further down the road make sure you do your research and find one that is right for you.
Look up setting up a refugium sometime down the road they can be greatly beneficial in controlling your nitrates and phosphates. For your setup assuming you are going sumpless you could modify an AquaClear 110 filter to be a fuge look up: DIY AC110 Refuge online. You could also rig up a setup like i have on my 20 gallon to where the fuge sits level with the display and you draw water in from the display to the fuge and the fuge has a siphon tube that automatically keeps the two tanks level, very simple and effective. A third option is to buy a hang on back style dedicated fuge like the CPR Refugium that you can get online.
Hope any of this helps.
Shawn
