I'm in my 6th decade of being an American living in the U.S. The only place where I've ever heard of tipping front desk personnel is Las Vegas, where a $20 bill will, indeed, get you a better room. Of course, in Las Vegas, everything is for sale, and a well-placed tip can get you in to a sold-out show, a table in a fully-booked restaurant, etc.

Here's how I tip (and I've lived in Southern California for 25 years):

Restaurants - between 15 and 20%, depending on the service. The tip is usually NOT included in the bill, unless it is a large party (more than 6) that are dining.

Bars - the same, unless the bartender or cocktail waitress is particularly friendly, in which case I might tip more. The only exception is airline club rooms, at which I tip $1/drink.

Bellmen - $2 / bag, more if a bag is particularly heavy or awkward.

Taxis - 10% of the meter, more if the driver distinguishes himself, e.g. we get into an interesting conversation, he goes out of his way by helping with bags, etc.

Valet parkers - Dependent on the charge, if any. At least $2, frequently $3.

Concierge - It depends on how hard they work for me. Normally, I would not tip merely for making a reservation, unless a specific reservation was difficult to obtain and the concierge had to apply personal leverage to obtain it. I do tip for show tickets as these almost always required the aforementioned personal leverage. I do not tip for directions, recommendations or being given a hotel map -- these are all part of the job of a concierge.

Self-serve establishments, take-out food, etc. - As a rule, I do not tip, whether or not there are tip jars.

Lounge singers and musicians - I'll tip if I think they're really good. I've tipped between $1 and $20, depending on the establishment and how much I like them (this is true around the world). I do not tip entertainers who approach my table to perform without asking.