Maybe you're wondering why one would want to impress a tea merchant/farmer/lover? It's not for vain glory or for showing off. When you meet an experienced tea person, you want to connect with him and, hopefully, get the opportunity to drink some of his better teas. The more you impress, the more likely to get treated with really top quality leaves.
Motivation and interest matter a lot. This is one reason, for instance, why it's not so easy to order from my selection. I only want to provide my good teas to people who are really interested in tea and take the time to browse through my blog.
Bragging about the teas you usually drink or the money you spend on tea/teaware is not the way to go. First, what you can do is show that you come with your own professional tea accessory: a porcelain Chinese soup spoon. (I must have posted about this long time ago already. I got it from one of my first classes with Teaparker). A variation would be to insist on using a porcelain gaiwan (or a competition set) to brew tea. (Later, if you do get the 'pro' to share some of his rarest leaves that are not for sale, you'll happily agree on using a teapot).
Often there will be 'tests'. A tea is poured in your cup and you're asked to say a word about it. Yesterday, I was impressed when my guest recognized that the puerh I served him came from Lincang. And I think he was pleasantly surprised, too, when I told him that the puerh he had brought tastes like Yiwu (as it came from Yiwu). The answer to such questions shows your level of tea expertise. If you can't precisely tell the region, then you can broaden your answer and give a more detailed account of your tasting. If your description matches the tea well and you show that you appreciate the tea's quality's and/or recognize its shortcomings, then you'll earn respect.
When you're making a new tea friend and you hope to drink some of his best tea, it seems also logical that you would be willing to share some of your own best leaves. This is always a touching gesture. And it could lead to some healthy 'competition', where the other tea fan will try to find a tea to top yours. Some special leaves can be real door openers.
Maybe you'll get the opportunity to brew your tea yourself. A good brewing technique and a good result will earn you additional points.
Some tea fans can also be impressed with special accessories: an antique cup, a zhuni or a silver teapot, a handmade pottery... But, here again, it's not the mere possession of the item that will impress most, it's your intimate knowledge about it and understanding how (well) it interacts with a particular tea.