From the Beginning
I would always recommend looking around for a second hand setup because most of the time they come complete with all the equipment. Some also come with substrate and decor and for a much lower price than a new tank alone.
Another advantage of buying second hand is that you can change the appearance to suit your room. For example if the stand and hood are wood then you can paint or stain it however you like or even alter it knowing that you did not pay out loads of money. You can afford to be fussy when it comes to picking what sort of tank you want as there are so many good second hand ones out there to choose from.
One of my Haplochromis tanks was bought second hand but I had to have the stand and hood custom built because no matter how much I looked I could not find a solid six foot stand to replace the damaged one that came with the tank.
Not all second hand tanks come clean so the first thing that I do is wash the tank with nothing more than clean warm water and a new sponge. You can partially fill the tank now and check to see if there are any small leaks which is always a good thing to do especially with bigger tanks. If you find a leak then leave the tank to dry out thoroughly before sealing the leak with some silicon sealer and always leave the sealer to properly dry.
Once happy with the tank I turn my attention to the hood and stand. This is when I would clean, repair or even change the appearance of it depending on what I want it to look like. If the tank did not come with any polystyrene sheets then make sure you purchase some to place on the top of the stand. These are there not only to keep some heat in the tank but to protect the bottom of the tank from any abnormalities on the stand. Juwel Aquariums do NOT need polystyrene. Another tip is that if your hood is wood and has no light reflectors in it then you can line it with tin foil using wood glue. This is a cheap way of reflecting the light into the tank without the expense of buying reflectors.
If your tank came with equipment then you now need to check this to make sure it all works. There is nothing more annoying than finishing your tank and finding out that something does not work so you have to run around trying to find a replacement. You can check all the electrical equipment by placing it in a bucket of water and turning it on. Never test any equipment out of water. Some of this equipment will require cleaning so carefully clean it with a sponge or toothbrush and nothing more than warm water.