I think the best way to aquascape your tank is to spend some time getting to know your rocks
Take a while to look at the rocks you have. I found that I would look at the tank and think "that rock would look better standing up/over there" etc. If you're happy with the overall shape of the rockwork then tinkering with the position/orientation of you rocks could be all that's needed.
I think there are some basic "shapes" when it comes to aquascaping a marine tank.
1. The Wall - As it sounds, a wall of rocks stretching pretty much the whole length of the tank. I personally think this looks better if it's not too uniform in height. It's probably not the best way to scape your tank IME as you can't see the back of the tank and it takes alot of room on the floor of the tank so you limit your substrate space. Another thing to consider is that when you have a "wall" you don't get very good water movement over all of your rocks, this could theoretically have an effect on filtration.
2. Two Islands - Again it's a pretty simple idea. Pile the rocks into 2 seperate mounds. I personally think this gives the best aesthetics. It gives you lots more scope for coral placement than a wall arrangement and you get much better water movement around your rockwork. I have found that it makes the tank look more open and more spacious and gives you a central sandy area. I try not to pile the rocks too tightly and leave some holes in the islands so I can see pretty much all the tank. One benefit is it gives definate territories for your fish. I find my clownfish lives inside the left hand island with the peppermint shrimp and cleaner shrimp. My damsel and cowfish both sleep in the right hand island with the goby. All the fish hang out in the calmer central area in the day.
3. Atoll - Basically one large island. This works best in cube tanks IMO but it can be done in long tanks too. Has the same benefits as 2 islands. The atoll could be in the middle of the tank or placed to either side. It would give the maximum sand area if that is a consideration for you. With some creative scaping you could create bridges and caves underneath to provide hidey holes and maximise water flow.
4. Lagoon - This can be either L or U shaped and tends to work better in bigger tanks. Basically you create a L/U shaped wall with a central protected area. This is good if you want to keep low-flow loving fish/corals with higher flow species. I have also seen this done in bow-front aquariums to great effect.
How you decide to scape your tank all depends on a combination of personal taste and what you plan to keep in it. I personally started with a wall shape and have recently changed it to 2 islands which was a great improvement. I then moved a few more rocks to create a small wall between the islands which has formed a kind of lagoon effect
This was our wall scape
This was my first attempt at the 2 islands look
This is it now...
A bit blurry but you get the idea
