How to calculate a grocery budget?

Ok so my friend and I are going to Purdue this coming fall and were sharing an apartment... I love to cook and plan on making my own breakfast, lunch, and dinner pretty much every day! (eating out cost way to much and isn't healthy!!!!) Nothing super fancy but also not as simple as opening a can of soup... I mean... I want to be able to open the fridge and say hey! We have some chicken breast, swiss cheese, and ham! Lets make chicken cordon bleu! Or hey, we have the fixing for homemade alfredo!!! IDK... Basically like at home!!! Anyhow... I just don't know how to go about planning a budget for the groceries!!! Like... Obviously I can plan out what I'm going to eat every day for the next nine months!!!!!!! But I would like to know roughtnly how much to budget for food!!!!!! Also I have never lived with someone else before... What would be some good ways to share the priice of food!?!