For me it depends upon how long and varied the wantlist is. If it's short and/or limited to one or two issues you can probably eyeball a dealer's stock as quickly as he can help you. EXCEPTION: A high end item that he has stored away behind his table. If your wantlist is long or "shotgunned" with lots of issues then it's mush easier to let the dealer see it; he knows what he has. BUT IMO give him a list WITHOUT the prices you are looking for; keep that list to yourself. If he's got an item that you want and his price is lower than what you'd be willing to pay he's more likely to quote your price than his.
I'd make a list in a small notepad or maybe on your phone. Then I'd browse the show, if you find a dealer who has the quality you're looking for but don't see the coin you want in his case, ask him if he has said coin but isn't displayed.
I agree with making a shorter list. One thing I would do is ASK. Too many people just browse past tables and only look to see what is out. Many times dealers have a lot more stock with them, but no room to display it. Many of my best purchases from shows was from asking about a certian coin, and the dealer reaches behind him to get it. If you have longer lists, those are best to send to dealers afterwards.
Make the list relevant to the dealers you want to share it with. In other words, if you are looking for high grade State Quarters, gem type and circulated colonials then show me only the gem type list since that is my niche. Then, show the modern guys the State Quarters list and repeat as needed. It can be frustrating to be busy at a show and have someone ask for something that a dealer clearly does not carry.
I understand you are a dealer sir, so more knowledgable than I on this, but I slightly disagree. If I hadn't asked a bullion dealer if he had any ancients, I would have never bought a ChAU Ostrogothic gold a few months back. Very often dealers get stuff that does not really fit their main line. Are you saying that even though your main business is gem type, you may not happen to have some world coins, ancients, or circulated US coins occasionally? As long as someone is polite and does not interrupt another sale, I do not see how it hurts to ask, (nicely).
What I am writing about is when someone stops by the table and hands me a list of modern Chinese coins he would like to purchase even though I only have US coins out and my specialty is US coins and after I politely tell him that I don't have anything he continues with playing twenty questions about where I might have a Chinese coin put away and hidden (true story). I am also writing about dealers (many) whose eyes glaze when the are handed an overflowing want list and they can tell it isn't their niche (it happens often). Lastly, I was specifically tailoring my answer to the OP, who seems to be going to his first large show and may not be organized, may not have a good strategy and will likely know few dealers. In this case, his time is especially valuable and he needs to limit the frustration that repeated rejection may cause.
I understand sir, but I was just reading your response generically for everyone here. Clearly your examples are absurb, but if I walked up to your table seeing nice US coins, is it out of place for me to nicely ask, when you are not busy, if you might have some world or ancients? That is all I am saying, just because a dealer may not be displying something, it does not hurt to ask if done when he is not busy and in a nice manner.
I frequently am able to pull a coin from behind the table to satisfy a want list, but cannot do so if I cannot see the list. If the list is manageable . . . say 20 items or fewer, a 15 second glance is all I should need to tell the visitor if I have a coin worth looking at.
Doug, I showed a dealer the list I brought with me because I was looking to fill a hole in my Morgan collection. I just happened to "know" him from the NGC boards. "Know" = traded PM's on a previous internet purchase from his company. Long story made short, we used my list to find an appropriate Morgan in his inventory that met my needs. We were able to use the list to shorten the time necessary to finalize the transaction.