Everything Kwilia said and...
What about sanding the walls and wiping them down in order to create a clean surface the paint will stick to?
Are you changing colors? If you are putting a light color over a dark color, you probably need a coat of primer first. If you are painting with a dark color, you will probably need to plan for several coats of paint.
Prep first, then ceilings, then edging, then walls, then windows, molding and baseboards.
I would buy several plastic paint trays, extra roller inserts, a fair sized paint brush to do the edging and corners, a smaller paint brush to do the windows, molding and baseboards.
Good luck!