When a group goes out to dinner, I think that it is easier to divide the bill evenly if you have comparable meals. If I a more expensive entree, I will pay more. Most places where I eat, an alcoholic drink and a soft drink are almost the same price. I think that it is better to overpay than underpay anytime you go out. Luckily, when I go out to restaurants, it is usually with my boyfriend who would never consider letting me pay.
Another way to combat this problem is to go to a restaurant with fixed price menu. That way the bill is the same for every person.