It would be very nice if eating out were free. In reality, someone must pay for the dinner as well as the tip to the servers. Paying the bill and leaving the right tip are very often an area of concern or confusion. This should never turn what was a delightful dinner into a quagmire or uncomfortable scene.
In general, if you are invited by someone out to dinner, that person intends to pay the bill. The tides begin to turn, though, when groups of people decide to dine out together. In this case, the rule is that each person, or couple, is responsible for their portion of the bill and tip. The expression traditionally used is "Going Dutch". It sometimes gets a little tricky- especially when each person's math skills may be a little shaky. Sometimes a person will add up what they had using the prices on the menu- but fail to consider the sales tax. Without a calculator, it is difficult to figure your portion of the sales tax. You most definitely do not want to come across as selfish or stingy. For instance, if your portion of the bill is $20 in menu items, and the tax is 6%, you should round up to the nearest dollar for the tax. If anything, that portion over the true amount would wind up as more for the tip to the server- and unless the service was poor- that is never a bad thing. If you cannot afford the extra cents, then you should not be going out to dinner in the first place.
Sometimes, someone will grab the check and offer to pay. Unless that person has invited you to dinner, never assume he or she is paying for dinner. Instead, each person or couple should politely ask to see the bill so that they may pay what they owe. If the person who grabs the bill says he or she is "taking care of it", there is always some sort of friendly bickering about that- because no one wants to seem unappreciative. It is also their way of showing humility. However, if the person insists, again, that they wish to pay the bill, do not go back-and-forth in an argument. Be gracious, polite and express your appreciation. You may wish to say that the next dinner is on you. In this case, this process goes smoothly, no one is insulted and the evening can end on a very pleasant note. Keep in mind, though, that if you say the next dinner is your treat- you MUST pay the bill the next time you dine with this person or people.
Leaving the right tip is another area which can cause confusion. This is because there is a great deal of flexibility involved in tipping. Some restaurants include the tip in the bill. If this is the case, it is stated on the menu. Be sure to take note of this so as to avoid double tipping. You are free at your discretion, though, to add to the tip if you feel inclined to do so. The traditional amount to tip is 15% of the bill before the tax. That is the minimum you should expect to pay if the service was appropriate. More and more people today tip at the rate of 20% of the bill before the tax. Some choose to include the tax when calculating the tip. Some, again, choose to tip a greater amount for extraordinary service or because they are very generous. In any case, be sure that you tip at least the minimum for good service.