Should you tip?
Yes, if the service was acceptable. Many jobs in the service industry pay very little. Without tips, these workers would have a hard time raising a family.

Who should you tip?
Just about anyone in the service industry. Including, but not limited to, non-fast food restaurant workers, barbers, maids, taxi drivers, bartenders, and webmasters of conversion sites. ;)

How much should you tip?
The generally accepted value is 15% to 20%, though outside North America it may be different.

If service was poor, do not tip anything. If service was ok, tip 15%. If service was great, tip 20%.

How do you figure the tip without a calculator?
So, you're at your favorite restaurant without an Internet connection and you left your trusty calculator in your other pocket protector? All is not lost, there is a somewhat easy way to calculate the tip.

15% = 10% + 5%. So what you need to do is figure out 10% then add half (5%).

10% is very easy to calculate, you just move the decimal place one to the left. For example, if the bill is $25.00 then 10% would be $2.50.

Then to figure out 5%, just take half of that, which would be $1.25.

Now you have 10% which is $2.50 and 5% which is $1.25, add them together for a total of $3.75.

Often, the bill ends up at some obscure value such as $17.73, which may be a bit difficult to calculate using the above method. In cases like that, just round it to the nearest dollar. It would be much easier to calculate the tip for $18.00.