It takes patience. Simply look at the rock you have, find rocks that have flatter sides that will lay securely on each other and can't be knocked off later on by aggressive fish or large snails. Take your time and evaluate the shapes. Do not hold the rocks out too long in the air, use a bucket with tank water in it to hold them as you evaluate. Put larger on bottom, vertically and horizontally; wider at bottom so you can pyramid them. It is more interesting to have an asymetric allover shape than otherwise, making one side of your tank higher than the other. Make lotsa holes, in between areas of larger and smaller rocks. Fish need security places. Read before putting just any fish together and be cautious of knowing your invertabrates and corals. You will have a great tank if you are patient and get the right info before stocking. Your tank needs lots of weeks to prepare for live critters. Please don't get a mandarin until a year has passed. They need to feed continually and adding brine shrimp, which they do eat is useless in keeping them alive. I added that tidbit of knowledge because I get really disgusted at hearing about stores selling them to new hobbyists. They need a mature tank. Oh, do not lean your rocks on the back of tank. Pressure not good for the glass. Enjoy! It is an art to build a good tank. When I figure out hoe to use my digital camera for my tank, I will show it off. It is beautiful and was well worth all the educating myself.