Cultural traditions, salaries and expectations are very different from country to country and the answer will be very different according to that. Reading a blog entry written by an American one will be instructed to tip everybody at every moment, from the person who cuts the hair of the pet, to those working at the reception of a hotel, to the guy who calls a cab. The justification is that many of these workers are underpaid (somehow a weird justification in a country that prides itself on being the example of honest wages and justice). If the entry is being written by someone let’s say from some of the European countries or Latin America that advice may be not to tip at all. I personally like to hit a middle ground.
My understanding of tipping is something given as a sign of appreciation for someone that is offering exceptional service. I have problems to accept the fact that I am paying a very expensive night in a hotel, where there is even a service charge included and I still have to leave a tip, otherwise those working there will not be as friendly with me and even the cleaning service will be less than acceptable.
I hate to admit that in many countries gratuities are not such a thing, but a mandatory charge being forced to pay unless one wants to experience a very awkward moment. My approach to tipping is always to immerse myself in the general culture of the country, to read a lot of what is expected and to take my own decision. In countries such as United States when I am in a restaurant I tip, I know that those working there are underpaid and it will be bad for them not to get the extra cash, but I still do not like the fact of knowing that employers are shorting them on wages and relying on me and on the fact that I do not want to have an embarrassing moment, so I will leave some extra money for them.
I may leave a token of appreciation for those cleaning the room, I always try keep the room as organized as possible so they do not have to work a lot more than necessary, I may give something to an exceptional concierge, but to expect that I will be tipping someone for checking me in (in other words for doing their job) that is too much!
Not every country thinks in the same way as the United States, in many places service is already included in the bill (and this is how it should be) so the fact of tipping where it is not customary for locals in place of being something good can actually create a conflict for those living there. As I said I am a good friend of transparency in bills, a service charge should end in the hands of those providing service not in the pockets of the owner.
I like to travel, and I believe that traveling is a good way to create jobs, and help local progress. I do not think that tipping is the solution to unfair employers and underpaid personnel. Gratuities should be that, something that is not forced but something that comes as a gesture out of generosity, at the end when I am in a hotel, or in a restaurant they are not providing free services I am receiving a bill, I am being charged for something. Employees should be paid fairly and this fact should be the responsibility of those hiring them, final bills should be that, a final bill, travelers have the right to not expect hidden or forced charges coming out once the final bill has been paid.