I do not go out with people very often. Sometimes they've paid for Herrick but that's when I paid for their concert or movie ticket.
99% of the time when other people are in on the food, it's a lunch order at work. We always figure out what we owe and send The Orderer the money. This is very easy to do. Just go on the website, make your own order, look at the total and send that amount to The Orderer.
If I give them cash, I do not expect to get exact change. However, If the meal is around $15 and I only have a $20 bill and for whatever reason The Orderer does not use money transferring apps, then I prefer not to be in on the order and just get my own food.
Phoenix87x bringing the exact amount for his own food is perfectly acceptable methinks.
Edit: I voted for separate checks but I think having one person pay with a credit card & sending them money or giving them cash is basically the same thing. I'd rather not ask for separate checks especially if it's a large group.