Sharing plates
I love this eclectic style of dining. Sharing plates are convivial and social. The main drawback is that sometimes all the dishes you have ordered turn up to the table at exactly the same time. My heart sank the first time this happened. What we'd expected to be a leisurely two-hour dinner was over in less than thirty minutes. These days, I stay one step ahead of the kitchen by ordering sequentially. If we're after, say, six sharing plates, we order two of them and don't order the next couple of dishes until we've eaten the earlier ones - and so on. Some waiting-staff seem uncomfortable with this strategy but I'm even more uncomfortable about being served our entire meal five minutes after ordering.
Oversized plates
Sometimes very small quantities of food are delivered to the table on very large plates. It's a case of style over substance. When tables are small (or, say, four people have been seated at a table for two) this approach to plating really doesn't work. It's quite perplexing when waiting-staff bring a plate of food that clearly will not fit on the table. Sometimes they stand there, expecting diners to rearrange candles, condiments, glasses, side plates etc. Skilled servers, of course, would clear a space ahead of time rather than manufacture an emergency. Once or twice I've taken it upon myself to rationalise the plates involved. "I don't think this small bowl really needs a dinner plate beneath it," I've been known to suggest helpfully in the interests of being fed.
Communal dipping sauces
We all know that double dipping is not acceptable. One must not, for example, take a bite of a spring-roll and then dip it once more into the communal sauce which accompanied it. That's just germy and guaranteed to rile your more refined dinner companions. To avoid being associated with even the suggestion of double dipping, I have acquired the habit of directly pouring some of the communal sauce onto the side of my plate. I don't know if this is acceptable or not but it does mean I can dip away with a clear conscience.
Faux plates
While I'm complaining about plates there's an entire subset of people for whom a plate represents luxury. These are diners who wish to never eat off another chopping board or out of a flowerpot ever again. The "We Want Plates" Twitter account documents some truly hideous ways of presenting meals.
"Helping" with the plates
I've seen diners pick up plates and hand them to waiting-staff when they come to clear the table. The diner is probably only trying to be helpful but I suspect it's more helpful to allow the person clearing the table to figure out how to execute the task. Foisting a plate upon someone just because you want to get rid of it is rude. Similarly, never scrape leftover food from plates at the table. Also, refrain from stacking used crockery. As a paying guest at a restaurant these are not your jobs.