Here are my five points, some (maybe all) of which seem obvious . . . but still might bear saying explicitly.
1)
Know what you are doing.
I don't mean learning the details of the marketplace, like Les discussed (although that can be important, too). I mean know
what you are doing when you purchase a knife. Why are you doing this? Are you collecting for pleasure / as a hobby? Or are you really hoping to turn a profit? Because there are a lot of knives I would never have purchased if I was hoping to turn a profit on them. I bought them because they appealed to my asthetic tastes and furthered what I hope to achieve with my collection. What kind of collection are you trying to build? Do you want to collect a particular maker or groups of makers? Do you want to collect knives of a particular style, or made a particular way, or having certain design features, or having certain handle materials, etc.? Do "art knives" appeal to you? Or are you more interested in knives with strong performance characteristics pertaining to the heat treatment, the metallurgy, the grind, etc.? Are you interested in true one-of-a-kind knives, or are you more interested in classic or even iconic knives that have been produced in quantities by certain makers (e.g., Loveless Big Bear; Fisk Sendero; Moran ST-24, etc.)? When your collection is mature, what do you want it to look like? To me, EVERYTHING flows from this - from knowing what I am doing and why I am doing it.
2)
Ask yourself how each piece you are considering purchasing compares to similar pieces you could obtain elsewhere.
Is there something about this particular piece that appeals to you? What is it? Are there other alternatives that provide the same appeal which you might consider as alternatives? When you set this piece alongside the other knives in your collection, and you look at them all, will this knive make sense to you? This relates to Kevin's point above about not buying a knife on impulse.
3)
Don't ignore any commercial channels for obtaining knives.
I have purchased knives directly from makers, I have purchased knives from other collectors, I have purchased knives from purveyors, I have purchased knives at auctions, I have purchased knives from eBay (yes, I have), and I have purchased knives from listings at websites like Blade Forums and CKCA. I cannot say that any one way to purchase knives is always the best or offers the best value or satisfaction. However, your answer to the question in point (1) above may restrict the channels available to you, for example you may want to do something so unique that the only practical way to further your collection is through direct orders with the makers to produce the unique knives you seek to collect.
4)
Don't spend your mortgage or retirement money on knives.
I said that these points seem obvious. But I have seen too many posts over the years with folks "needing" to sell their knives to pay bills, or who had to dig out of debt after spending too much money on knives. I suspect that in most cases these folks do NOT get as much money for these knives as they paid for them, and this is sad. Unless you are collecting knives as a business venture (and is that reallly "collecting"?), then this is a SPARE activity that IMO should be done with SPARE money that does not threaten your fulfilling your responsibilities to your family, your other creditors, etc. Of course things happen that no one could have reasonably foreseen that can change things for you. But IMO, you should really try to foresee what can be reasonably foreseen and act accordingly.
5)
For my first few years of collecting I took a solitary approach, however really started to enjoy the experience much more after I started interacting with other custom knife enthusiasts through forums, joining organizations and such.
Yes, I plagiarized that from Kevin. But I could not say it any better . . . so I stole it (with attribution, of course).
