I have had the good fortune to dine at Le Francais in Wheeling Illinois years ago when it was in it's heyday. I was treated to the meal by the employers of a friend of mine who was their personal chef. There were four of us and the wife of the employer knew a bit about wine and started off by ordering 180.00 bottle of wine. After that first bottle there was an obvious shift in service. After she ordered the third bottle of the same wine the service had kicked into high gear with the Maitre'D flirting with her and everything. The whole experience made realize that you do get different service depending on how much you spend and how much you tip.
Over the years I have gone through many phases of tipping from mostly nothing to very high tips. I have now settled on the following. I start at 15% as a base and that is on the subtotal not the tax. I used to do the tax all the time. If the service is good I leave 15%. If the service is great I leave 20%. But when service really is outstanding I will easily leave a 50% tip or more. That being said I have had a few outstanding services but sadly few of them were in the United States. I have been very put off by the service in the US for the past couple years. Service does not seem to be taken seriously and more and more it feels like the waiter expects a tip and doesn't earn it.
Back to the original theme of the discussion though. I often do web related work for different restaurants in Chicago. Typically I prefer to do a barter for the work where I get a free meal etc. On one occasion I used the opportunity of the free meal leave a generous tip to the server ($150.00 on a free meal). To which the server came to my table in front of me and my wife and asked me why I did that. I told him I wanted to pass on a nice tip to him. To which he replied "that was completely unnecessary". I was shocked and I would never tip that guy so well again.
Regarding business lunches and big tips well to me your renting a table at that point and you should pay the staff. A 2-3 hour lunch costs the restaurant money when they can't turn the table and it is wise to leave a good tip. It is great to hear how well some of you tip for business lunches which I would imagine you can expense.