After trying many different ways to do it, I found that the easiest way, is to find similar dish on FS, eyeball the quantity (weight it if you can, or measure) and log it. It is better to guesstimate, than stop logging at all. If you have time and cook from scratch, you can weight the ingredients, calculate the calorie value of the whole dish, and then enter the portion you ate. I use nutritiondata.com to enter and save my recipes. Any way there is no foolproof way to log in food you had in a restaurant. Some of the chain restaurants have their menus published with calories in every dish, but I do not eat in chain restaurants. You were also interested in entering food from local restaurants, so that is not an option.
The first thing you lose on a diet is your sense of humor. ~ Author Unknown
It doesn’t matter what diet you follow… What matters is what makes you follow your diet. ~ Tom Venuto