First off, be ready to spend time doing this, it's not a quick job. When I got my 55 gallon it took all night to set up, and get the fish moved in. Now, sit down and read this once before you start, and read them again while your doing it. Why? So you can have an idea of what you have to do before you have to do it, and if you forget a step or important part, you'll have this to refer to. You don't have to do everything the same way I wrote it out, but if you don't know what your doing, it's a good idea, because some things are very important.
1. Place the tank on a solid surface that will support the weight of the tank once it is filled with water, and rocks, etc. Do not place it on the floor because when you go to clean the tank the siphon won't work. Also, try to avoid placing your tank in an area where it will not receive direct sunlight, this will cause algae.
2. Now, wipe out the inside and outside of the tank with a wet cloth, try to make sure the cloth is clean too. Be careful when handling a wet aquarium because glass can be slippery when wet. Do NOT use soap when cleaning your tank, and never rest the tank on it's side.
3. What I suggest now is putting on the background if you have one, (On the back of the tank, not on the inside) because putting it on after the tank is setup is a pain, I know hehe. Now, put the filter system on, but do not plug it in until the the tank has been set up and water is in it.
4. Gravel is good to have in a tank. If you do include gravel in your tank setup, rinse it good, because most gravel has dust or fine particles in it. Use a bucket or something like it to rinse it. Run water into the container while stirring it. Empty out the water and keep stirring until the water is clear. Now add the gravel.
5. Next, fill the tank with room temperature water. If you use cold water it may cause condensation and the tank will seem to leak. You can place a bowl in the tank on the gravel to stop the water from moving the gravel around. (I never had any success at getting the water in the bowl, so it didn't seem to help me much, might help you if you have better aim though.)
6. Add any decorations you have for your tank, if any.
7. Start up your filter, but, make sure you know what your doing when you do that, because when I first started my filter I didn't know what I was doin' and I probably almost ruined it, so, read the directions for it. Turn on your heater too, get the temperature to where it is needed for you type of fish.
8. Cycling your tank prior to adding fish is very important, this often takes weeks. This is allowing your tank to run until your water parameters return to 0. However, there are certain cases where you may not have the opportunity to cycle the tank.
9. Put the hood and lights on. After you get the temperature where it should be, put the bag your fish came in in the tank, and leave it there for 15-20 minutes, add a little of the aquariums water, and let it set a little longer. Then let the fish into the tank.
Take good care of your fish.... be willing to spend time and money taking care of them, good luck.