If the meal comes with chips, just ask for salad or veggies instead of the chips.
Salads are always good, especially now with the warmer weather. Order it with the dressing on the side, then you can pour it on yourself and decide how much you want.
Eating slowly is good too. Using your knife and fork properly (ie with the prongs of the fork facing downwards, not using it as a shovel lol) takes way longer to get the food onto the fork! And make heaps of conversation... hard to eat and talk at the same time
I always leave food on my plate when I'm eating out. Mainly so I don't look like a pig for cleaning my plate... but also means you eat a bit less. How many times have I had a waitress comment on how much I have eaten when they take away an empty plate
So now I leave a bit so they can't say anything...