[Por_sha911]

As others have said,
-I don't tip someone who hands me a bag at the register. That is not service. (I don't frequent a local place where I know the people).
-I don't tip before my meal is served. If asked, I advise I have cash based on the service when I am done.
-I do tip very well and have not problem with "suggested amounts" but refuse to be intimidated with the "chose 20% 30% or 50%" options.
-I absolutely check that the pre-calculated tips amount are not a % of the tax, and I do some quick math in my head to be sure it is correct (yes I have found some errors and they are always too much as opposed to not enough...surprise?).
-I will usually leave 10% when the service is BAD with a note explaining why. One time I left a penny with the note just so they won't think I forgot. No I didn't go back there.

Random side note: one time I paid cash at the register of a convenience store/gas station. I was handed my change but noticed that they only gave me bills but no coins. I mentioned it to the cashier and was told rather matter of factly that they don't "bother with the coins" and just round up. I looked around and saw no sign indicating this. I told them matter of factly that I bother with coins that due to me and want the amount they owe me! I suspect they cashier was politely stealing from the customers.