The tip is quite different, depending on how much you are "sat" and in which country you are. More or less a universal solution can be called the idea to give a tip of about 10% of the order total.
To leave a tip less than 5% is considered bad form and a manifestation of greed. There is a placket and on the other hand: one should not give a tip more than 25%. In Russia there is no tradition to give a tip fixed, so often people just leave a flat amount, rounding out what is written on the receipt. In this case, be sure to tell the waiter that I don't need change. Sometimes visitors of restaurants prefer not to say anything, just not taking the change, but here by waiters not quite clear, maybe you just forgot the money, and left them for tea.
Tipping in Russia is left in the case when the people in the restaurant liked it. If the service was excellent, the food is delicious, and the waiters are helpful, you should definitely leave a tip. You can even add in excess of how much you typically leave, to encourage staff of the institution. Usually if service is bad, customers leave about 5%, and if you are very good, the amount is often increased to 15%. More than 15% tips, usually only wasteful or drunk visitors.
There are rules of etiquette regarding tipping. For example, in Germany it is customary to tell the waiter that you are happy with the service, when you leave a tip. In Russia the established rules. There are countries where tipping is considered an insult, for example, is Japan. It is useful to clarify the traditions relating to tips before you go somewhere.
Some institutions put a box for tips at the cash registers. There's usually written something like "for a tip", but sometimes the waiters are creative come up with different funny captions to lift the mood of customers or to amuse them. I must say that this policy works, tips in these boxes accumulate much more.