Kray2s,
The only thing you can really do is try to educate yourself as much as possible. I play on the Atlantic shard which is supposedly the most populated shard. Prices for items are highly inflated because of the number of people (I'm assuming here) but there are still a very good number of people buying and selling here.
I usually lurk in this forum to watch what is being sold for how much. Just for some education for myself, this weekend I spent my time touring other shards. Yesterday I toured 4 shards and today I have done 3. I picked a few shards that I know are very quiet and a few that I know are still very active. I checked Zento, Luna and one or two large areas that I know there are vast quantities of housing. The first 4 shards I did quite abit more travelling. (All these spots are full on Atlantic).
On more than half of the shards I checked, I could place keeps or 18 x 18's. I could place 1 Luna house and 3 or 4 Zento houses. On one or two I think I could place castles. On more than half of the shards I checked, there are none or very few smaller houses placed in most areas, only bigger houses like 18 x 18's, keeps and castles.
Since I have no developed characters on any of these shards, I created new chars with 50 magery and turned on the "Warn of Reagents on the ground" feature of UO Assist.
What started as a way to recall to different areas to look at the general population of each shard soon turned in to what I now call the Pumice Meter. "Pumice Northeast" "Brimstone Southwest" Just about every time the meter went off, I could walk into the house in that direction and find a "Rare" collection.
Surprisingly or perhaps not so surprisingly, 95% of the houses were filled with water buckets, open books, diamonds, sashes, event robes, event sashes, trays, pitchers, ceramic mugs etc.
I saw many more two story statues, ploughs, & ruined paintings than I've ever thought possible. On the shard that was the least populated where I could place just about anything I wanted, there were 8 or 9 of these houses.
So my advice to you if you are intent on collecting rares is do some touring of your own. You'll soon see what is rare and is not rare. It used to be that having a house full of these "rares" did mean prestige but in most cases in the years past, having a community location and events for your shard or providing a service for people will bring you much more gratification in that regard and keep your account safe.
On your tour, you'll also be able to spot the vendors that sell tokens & bods kits by the 100's because they are on almost every shard. Stay far away from those. Do not put a vendor in a house that contains one. A warning was posted to the Atlantic shard forum recently about a certain token vendor selling tokens bought with stolen credit cards. Those vendors are in Luna on almost every shard. According to the warning, they did wear green and blue robes but most have been changed to dragon armor now since the warning was posted.
What was very evident to me on my tour was:
1. A very great many people are leaving or have left uo. The sheer number of falling houses and empty spots on these shards is alarming.
2. There are a great many more "rares" than there should be. While I am sure there are still a few legitimate items left, it is painfully clear that most are not rare. This pains me because most of the lower end ones are the ones that I have collected over the course of 10 years to make my public building "special" too. At one time I aspired to be added to the Museum sticky thread here but now I see there is no point to it.
3. Sadly real rare collecting has been pretty much wiped out by Character Transfers in more ways than one. Shard specific rares should never have been allowed to leave the shards they were intended to provide a history for and of course x-sharding provided the means to dupe. What you see now is mostly profiteers only concerned with how much they can make, uo good or rl$. Very few left are concerned with community or shard history.
Sarsmi said it best in a post that was unfortunately deleted by a mod. The jist of which is you want to deal with a trader/collector/dealer that will be honest about which ones have been duped and are concerned about not passing on these items knowingly to you.
Make your buying decisions as informed as you possibly can now and in the future as it is much more than the present moment that you have to be careful in the world of rares. EA at any time can make any item worthless by changing it to a common item or illegal to own and ban all your accounts for selling or possessing it/them.
Caveat Emptor....