They’re servers, not servants
You might think you’re being helpful, but the most helpful thing you can do is allow waitstaff to do their job. And as it’s their business to be accommodating, the very least you can do is not catch an attitude. It is their job to be polite, so if you’re being rude to someone who can’t be rude back, what are you really doing? Just being a bully? Human beings are thoughtful by nature! Don’t forget that just because someone’s waiting on you for the night.
When the host is busy, it can be tempting just to seat yourself and save him the trouble. This might seem like helping, but it might be making his job (and the servers’ jobs) more difficult. Hosts have a system for distributing tables that keep the restaurant running smoothly. If you see the host is busy when you arrive, wait a minute or two before hailing someone for attention.
Stacking used plates at the table
Full disclosure: I did this all the time. I thought I was doing servers a favour, but it turns out it’s icky and inconvenient. Leave your plates as they are – your waiter has a system for clearing the table.