Diversify But Do Not Be Greedy.
There are literally hundreds of different investment options out there and some of them are not even scams, pyramid schemes or ponzi schemes. The general rule of thumb is "If it looks too good to be true then it probably is.". Everybody who has a retirement "opportunity" for your money has a very good sales pitch for why you should do it. When encountering a new opportunity the first thing I do is to read around the subject. Look for the business name with the BBB (Better Business Bureau), check out other people offering the same thing and, most important of all, figure out where they are getting their money from. Once you understand the industry from their perspective you stand a better chance of not getting scammed. Be careful of get rich quick schemes and shady deals, remember that it is more difficult to scam an honest person and if it does not feel right then do not do it.
My mantra is "Diversify but do not be greedy" which can be translated as "Do not put all your eggs in one basket". It is better to have small amounts in multiple accounts than to put everything in one big account. Think about how many people have their entire retirement in one company, these are people you see quoted on the news when a financial institution goes under. Do not be like them, money is like fertiliser in that it only works if you spread it around.
Traditionally we think of a retirement account as something that slowly builds value over the years. This means we are used to seeing our retirement account value slowly grow over time. However, the only thing that is actually important is the value of the account when we actually need it. What account would you rather have? One that grows rapidly until just before you retire and then crashes down to zero? Or one that goes up and down over the years but ends up spiking to a new high just as you retire? Nobody can predict the future and nobody can guarantee that any investment will produce good results so the best we can do is to avoid the scams.
One more thing to consider is the timeframe for your investments. When are you going to retire? Ten years? Twenty years? The timeframe is important because it can affect how you invest. Decide when you will want your money, the shorter the timeframe the less volatile you want the investment to be. The trick is to not get caught needing the money when the investment that the money is in is at the bottom of its value cycle. You want to be able to pull the money out when it is close to the top of its value.
Unfortunately some types of investment such as real estate require you to be an "Accredited Investor" which, in legal terms, means that you need to have a net worth of over $1 million dollars or an annual income of over $200,000 ($300,000 if joint). I have avoided discussing those types of investment simply because this website is aimed at those of us who have less than that.