It might sound obvious but the first rule would be buy the cheapest gold you can. This means shopping around and a lot of browsing and comparing notes to find the best deals. There is a difference between dealers when it comes to coins and small bars and also take into account the shipping and handling charges which can also vary between dealers and mints.
Gold Bars, Krugerrands and sovereigns are perhaps the best buy with gold bars having the lowest percentage premium over the spot gold price. When comparing dealers and mints, compare the percentage over the premium and look at what is the bottom line. What is the total you would have to pay from each dealer for the same coin or bar delivered.
Buying regularly is another little secret to building up a healthy gold investment portfolio. Even if it is only a small amount each month it is surprising how quickly that small amount can become a substantial gold investment.
A good and thorough understanding of rare gold coins can also reap some spectacular rewards. Scouring the auctions and coin clubs can net one a good deal, particular if someone is in a tearing great rush to sell during a time of economic turmoil.
It is often said that one should buy low and sell high. But for the serious investor of gold who does not sell this is not the best way to go about it. In fact to continue to buy on a regular basis is more likely to conserve ones gold assets as the average price one pays for gold will even out over time.
If one wishes to trade in gold, then this is a different matter. It is more likely that one would speculate in stocks in gold companies or exchange traded funds and then different rules would likely apply. Such as, for example, understanding the dynamics of the gold market and its relationship to inflation, a bear or bull market in stocks, financial instability and so forth. Regular week to week or even day to day trading is subject to more variables and market forces and requires a different way of thinking, not for the novice or those of a conservative inclination.
For the saver, rather than the speculator, coins and bars are a more conservative way of saving and, when done on a regular basis, can reward the investor with a very nice and healthy gold investment.