I send it back and give them a chance to fix it ... If it's unacceptable the second time, I talk to the manager and tell them what's wrong. 

Usually, the manager will either give me a chance to order another item without charge for the first ... Or even offer the other item for … Read more

For an excellent server I tip 20-25 percent. For a bad or average one I tip 15 percent. When at the actual bar I always tip the bartender a couple of bucks.

I once heard someone talking about service worker  (wait staff,  hair dressers, cab drivers, motel/hotel cleaning staff, etc).  She said "we should always take care of the people who take care of us."