If we had a giant space ship to travel to another galaxy in the search of a habitable planet, what would be the best logistics plan to embark in a X million year journey?

Assuming we have the giant space ship to travel. What would be the best way to produce our own food, water, use of waste, energy, fuel, etc. How would a community this big be managed? What kind of professionals would be required to be there, how would reproduction be controlled?