A lot of people see the constantly-increasing price of collectible firearms, and assume that guns must be a pretty good investment. Well, they really aren't. The stock market outperforms collectible firearms with ease. But if you want to buy guns with an eye to increasing prices, there are a few things I would suggest.

1) Know your subject. The more specialized knowledge you have in a particular area, the better you will be positioned to find the best and rarest examples.

2) Be discriminating for condition. The highest condition examples are always the most desirable. They will increase in price the most if the pattern becomes more valuable, and decrease the least if it becomes less valuable.

3) Be willing to sell things, or else acknowledge that you are either collecting or building a nest egg for your survivors to sell when you die (or both, typically).

4) Don't buy "commemorative" guns. They are worth nothing.