The only hard & fast rule about tipping is that there is no hard & fast rule. You shouldn't feel obligated to tip in every circumstance or to always tip a certain amount. Tipping is common in the United States, it is almost second-nature.. In some European countries, it is not so common or customary to tip people for services. In Mexico, not only is tipping customary, it is expected in return for a good service rendered. Most people working in the tourism / service sectors in Mexico rely on your tips to supplement their basic pay (which sometimes may only be $5 or $10 a day) and they give good service to prove that it makes a significant difference to them! Remember that the term "tip" means to ensure prompt service. My approach to tipping, in Mexico, as elsewhere, is circumstance-driven. I have always believed that if you take care of someone that they will take care of you. I always tip more than I should sometimes up to 40%, however I do understand that this is ridiculous to most people. I talked to a good friend who is from Mexico and he said that standard tips in Mexico are as follows:
TAXIS - Usually a standard tip is usually 10% of the fare. If they've provided a special service, such as helping you with luggage, waiting a few extra seconds or minutes, taking a route that I specify, or providing some useful nugget of information then give them a couple extra bucks.
RESTAURANTS - The standard rate is 15%, but this is very much dependent upon the type of restaurant, whether the service was exemplary, whether special requests were made or honored, a doggy bag for leftovers requested, or how long your party may have dallied at the table…in which case the tip might reach as much as 25%.
BARS - The Standard in most Countries is $1 per drink, however if your bartender goes out of his way to take care of you then you might want to tip more, especially if you want him to remember you the next time you come back.
GAS STATION ATTENDANTS - If all they do is fill my car with gas, then you should not be expected to tip. If they wash the windows, check the oil, fill the tires or do anything that would've constituted full service , then the tip might range anywhere from $2 to $3 USD.
SKYCAPS and BELLMEN - The tip here also depends upon the level of service and the attitude with which it's rendered. Generally, $2 to $3 USD per bag.
GROCERY CARRYOUT - The amount varies with the quantity of merchandise, how carefully the sacker packed those items, whether or not the same sacker helped me place groceries on the conveyer belt before checkout, and the care with which he placed the purchases in my car. Anywhere from $1 to $3 USD..