I have lived in a handful of roommate situations. And I have probably handled rent, utilities, groceries, household supplies, etc., slightly different in each situation. From these experiences I have concluded that there is no better way to do this. It is just important to figure out a method that everyone in the house understands and agrees upon beforehand.
Regarding rent and utilities, we basically split these up per person. Also the bills are not all in one person's name; while we all love each other, I think it does help us feel "safer" in a sense to know that we share the financial burden together in this way. (Our landlords would only put one name on the lease, which is understandable.)
When the time comes each month, the designated person will collect all the bills, do the math, and then post it for everyone else to see. Since the lease is in our name, and rent is the biggest check, everyone else pays us the difference of their combined expenses and their designated bill. If that doesn't make sense, and you want me to send you an example, just let me know. However, I am not by any stretch of the imagination detail-oriented, and I feel great peace to leave this mess to others.
Early on we figured that it would be easier to share some of our food. Five adults sharing one kitchen (one stove, one fridge, etc.) can make for crowded meal times, and we think, not the best use of our resources. Basically we share almost all suppers (whoever is cooking will let everyone else know if it's shared food or not...but 95% of the time, it is), and some breakfasts. Everyone will take a sandwich or leftovers or eat out for lunch. This begs the question, how do you shop? Well, we made a list. Just call me Jacob (I love LOST!).
Our list is actually pretty mundane compared to Jacob's. When we moved in, we had a little meeting and wrote down all staple items for the household. This includes groceries as well as other stuff like paper towels, cleaning products, laundry detergent, etc. Basically, stuff that we all use and, therefore, we knew it would be easier to have one or two instead of five different types of laundry detergent. We even discussed preferred brands, bargains, etc. Then Jeff did his math magic (he is one of the resident detail gurus), and figured an amount that each of us should contribute to the "community fund" each month. Right now that is $35 per person. So if we are out of milk and bread, anyone can grab a few bucks from the envelope and purchase these things. We return all receipts to this envelope, and then Candy balances it out at the end of the month.
If we purchase a grocery item with our own money that we do not want to share, we simply put our name on it.
If we are expecting guests for supper (other than the close friends who drop by often), we will let everyone know via a household calendar that hangs in the kitchen. I don't think anyone has ever verbalized this, but we all pretty much understand that if you're having someone over for supper, you will definitely share space and probably share food with the rest of the household. I guess in this respect, privacy is infringed upon -- but then again, none of us really wanted to live alone anyway. It's all a big trade-off.
My bro-in-law, Brent, has asked a very important philosophical question. I know this question rose from deep within him, from his primal connection to and empathy for the only other male in the house:
How many bathrooms do you have??
Well, Brent, here's your answer. We have 2.5 bathrooms. Jeff and I live in the master bedroom which has a full bathroom, there's another bathroom upstairs, and then a half bath downstairs. We know we wanted at least two...I think maybe it would be possible to live with just one, but not for us. We're not that crazy.