When you have that big dinner party or that open house or all those friends over for a bit of fun and games, you need to make sure you have the right amount of food. I know that with me anyway, I'm not so good at estimating what's a good amount of food for a crowd. Fortunately there are ways to remedy that and refine your estimating and cooking-for-a-crowd skills (which include more than just the amount of food you provide). If you can start with these simple tricks, then you'll be well on your way to throwing the best bash around!
The thing to keep in mind as you cook for a crowd is that it's always better to have more food than not enough food. It's never fun to run out of food when the party wants to continue partying on! If you're in doubt go for more rather than less and if you have leftovers then that's just more food for you that you don't have to cook.
When estimating, try to be realistic with your numbers; consider who you're inviting and always assume people will eat more than one serving. Living in a family and observing those trends is actually a really good starting point for cooking for your own crowds. With chicken breasts and similar items, cook one or two more than the amount of people you're expecting to allow for seconds. When making mashed potatoes or other vegetables, it usually works to assume one vegetable per person (you'll want to make just a bit extra to give yourself some wiggle room). You may have to double or even triple recipes, but it is less stressful to deal with leftovers than to try to whip something up when the real food runs out.
Something else to consider when cooking for a crowd is what to cook. Remember, you can't please everyone when cooking, so there's bound to be someone who won't like something that you make. Don't be upset if that happens. Your choice of food depends primarily on the occasion and then on the actual people who will be attending whatever function you're holding. If you know all the people well, then you can feel free to do basically whatever you want, but if it's a more general crowd try to have a myriad of dishes. Have a few veggie dishes for those who don't eat meat and a couple different entrees with a handful of side options.
You don't have to make sure that everyone likes something that you make, but you should give them options, especially if your party is big and you don't necessarily know everyone really well. Use common sense when deciding on your menu and your intuition will usually be a good indicator of what's good for your function and what's not.
So now you're ready to embark on your cooking-for-a-crowd adventure. You know how to start portioning and you also know the basics of deciding what to provide your guests. With these basic building blocks you're set to throw the best party on the block!