My wife & I share our food. The normal restaurant portions are usually huge. We usually share an entree. We both watch what we eat. (should have done that years ago, but no time like the present!).

My point is that when the server gets the kitchen to split the entree onto two plates, the server gets a very nice tip (usually 20-25%). If the server explains that the kitchen will not put the one entree onto two plates, a nice tip is still given. If I explain that we are sharing the entree and only one plate is brought out, a lesser tip is given.

Sometimes, the server seems to dislike it when I mention that we are sharing the entree. Too bad, we eat smaller portions to get healthy--especially if we are on the road and don't have anywhere to keep the "doggie" bag. We order alot of salads because that may be one of the few healthy choices on the menu.

When we go somewhere like Las Vegas (this was more relevant in the old days when we didn't eat very healthy), we would tip very generously if the meal was priced alot less than a comparable diner. For example, if we bought the $1.99-2.99 casino special, we may leave a couple of dollars tip because the normal meal at a comparable place like Denny's would cost close to $10 or more. We would tip on our perceived value what it could cost outside the casino. I wonder if the eaters tipped on 15-18% of $1.99, how can the server survive on such low tips.

One thing I don't like when they have a share plate charge ($5-8) at some restaurants. If the restaurant would split up the entree & give each person the same amount of side (for us, veggies ^), we can justifiy the charge. If not, then not. What we do is order an entree & a salad. We then ask for another plate & we split everything. When we do that, it usually comes out just right.

I wish that people that wish to eat smaller portions be able to order from the kids or senior menu. Especially for solo travelers that are on the road & aren't able to keep the uneaten meal in a fridge.

Bottom line:

We usually tip the following:

Average job: 15%. (no extra plate brought out when we asked when we ordered the food--having to ask again).
Above average: 17-19%.
When the server splits the entree in half on each plate: 20-30%. Usually 25%

Even more tip when server does something special. I have done over 50% on a few occasions when the server went way, way above their duty.

If there are problems that are not server related (kitchen delays or extremely busy restaurant), I don't take it away from the server.