To err is human, and when you are dealing with hundreds of plates in the course of an evening, there is always a chance that a mistake will be made, or a dish will fall short.
If there is something wrong with your meal, do not hesitate to politely send it back. Restaurants want their guests to be happy, and every proprietor I know would prefer the opportunity to correct an error in the moment, rather than have a guest leave their dining room dissatisfied.
I know, however, that there are horrible urban legends about servers spitting in plates of unsuspecting diners that send things back to the kitchen. All I can say to allay that fear is that in my thirteen years working in hospitality, I have never seen anyone do this, and remind you, dear reader, that even in the myth, the server-saliva garnish tends to only be applied to customers who are rude and uncouth (Though if you do have any suspicion that a hospitality worker has interfered with your food or beverage in any way, I would encourage you to patronize an alternate establishment).
Should you find yourself in the position of needing to send a dish back to the kitchen, here are some quick tips to smooth what can be an awkward situation:
1 Be polite. Please and thank you go a long way.
2 Be clear in your desire about what would be a satisfying solution. Would you like the steak to simply be cooked a bit longer? Or is the salmon over cooked to the point of inedibility and a fresh filet is the only thing that will correct the error? Being clear from the beginning will help the staff correct the error most efficiently. If the dish is, according to the staff, actually prepared correctly and you simply do not care for it, do yourself a favor and order a different dish to replace it. There is no way to correct a braise once it is out of the oven, or take the minced onions out of the meatloaf.
3 Alert a server or staff member as soon as possible so the error can be corrected quickly.
4 If the dish takes a while to cook, a seasoned manager or server will ask if you would like to enjoy the side items while the protein is cooking, or they may bring you a complimentary sip of soup or a side salad. If these things are not automatically offered, it is certainly reasonable to request something of the sort, as having something in front of you will help any guests you are dining with feel less self-conscious about enjoying their meals while you wait.