Before you start purchase a good book from a reputable marine shop. There are plenty available, just search the Internet. I know books are very expensive but this purchase alone will save you time, expense and prevent you from making some big mistakes.
Reading useful threads on a forum will give you priceless help and information. Posting relevant questions that you are unsure about will save you money. There are no dumb questions, just costly mistakes.
Research equipment, make sure you are getting what you want and more importantly need. There is nothing worse than buying something and later finding you can get a better item cheaper, or to find you never needed it in the first place. Remember this Hobby is very expensive and mistakes are very costly. By saving here and there could save you hundreds. Just think, you could buy them prized corals, fish and invertebrates with the money you save.
Buy live rock, don't get grotto rock or glass rock, it is ugly, sharp and a waste of money. I purchased glass rock to save money on live rock. This cost £25 for a box. It ended up in the bin! That's two to three kilo of live rock.
Don't rush into putting livestock into your tank until it has fully cycled, I know you want to, but it truly isn't worth it. You don't want to loose all the money you spent on livestock.
Start small and build up to that all big admirable reef in your living room. This gives you time to learn about this fantastic hobby, mistakes wont be as costly. Starting small gives you the opportunity to build up your collection of corals to add to that new Dream Reef Tank.
Research your livestock, feeding, lighting requirements, and compatibility with other tank mates.
If buying on the web save on postage by purchasing multiple items together, livestock is very expensive to ship.
Find a reputable local fish shop. These will give you free information, check your water parameters, and only sell you what you are ready for. I would advise finding a local fish supplier from magazines such as Marine World. I would personally avoid other shops as these may stock many other varieties of fish such as freshwater, tropical, and so on. Marine shops specialize in marine keeping. obvious really. I would try a few in your area and find the one you think is best.
Don't be put off by the cost of this hobby, it is worth every penny, truly it is.
Always consult someone about health of livestock as soon as you notice anything strange. Contact your Local fish shop or fellow reefers on forums who will help. You may loose livestock if you don't.
Something i have done and costs nothing, Is to keep a diary of all the livestock and accessories you purchase with a date of purchase. This is very useful and helpful. Keep a diary of all your levels such as, Salinity, PH, Nitrate. Magnesium, Alkalinity and Calcium.
Take photos every few weeks and watch your reef grow, it's great to see things develop, grow and mature.
Probably one of the most important things to do is take it slowly. This hobby cannot be rushed, stocking of fish, corals, and invertebrates must be stocked over many months. Going out and buying everything in one go is a recipe for disaster. This will put too much load and strain on any form of filtration you have and result in tears. May be a total wipeout.
I Have compiled this article to help save fellow reefers time, money and negative effects of the environment. I have made many of these mistakes myself and felt they are worth sharing.