Probably one of the best kept gold coin secrets is that collectors can make money in rare coins by searching for rare coins which are undervalued and buying these during a time when the market is quiet.
Even when the gold price is rising it is still possible to seek out and find rare gold coins being sold at the gold value.
Rare coins, of course will tend to have a value in excess of the current gold price due to their rarity. Being able to buy at the gold price then will ensure a good return.
There are some important points to keep in mind however. One of these is the fact that rare gold coins are limited, By virtue of being rare there is a limited number available so the value increases due to rarity each year. this means they are harder to find and so more work is needed to seek them out.
Known what sort of coins you want to collect and focus on them. There are thousands of gold coins, rare and recently issued. Very few people are likely to be able to keep a track of each one so most people tend to specialize in a particular coin or group of coins. It might be a good idea to focus on a particular type of coin then, such as might interest you most. Such as the American eagle for example or the Canadian Maple Leaf.
There are also different grades of coins even in the rare variety so it is a good idea to get as much information and education on the types of rare gold coins there are and what the current value of each is.
Forming a good relationship with a Numismatic or coin collectors association is a good idea as one can glean information from them and get into communication with their members and exchange information, ideas and so forth.
The 1933 double eagle currently holds the record for highest price brought at auction for a single U.S. coin when it was purchased for US$7.59 million. 445,500 specimens of this Saint-Gaudens Double Eagle were minted in 1933, the last year of production for the Double Eagle, but no specimens ever officially circulated and nearly all were melted down, due to the discontinuance of the domestic gold standard in 1933. So although it is rare, it is possible to find rare gold coins.
As always, there is no substitute for patient due diligence and study. And probably that is one of the best gold coin secrets of all.