2) Eat a clean healthy meal like a tin of Tuna and some chickpeas before meeting up with friends. Stops you over eating and making poor food choices later.
3) Drink more water. A hydrated body preforms much better than a dehydrated one.
4) Carry snacks with you. Raw unsalted almonds or cashews are a good one. As are some protein powder you can mix with water.
5) Be the house chef. Not only will this make you more accountable for the food that you eat it will also save you a small fortune from eating out all the time.