Hall, Flow, Interior Doors
Halls make great transitional spaces, particularly as a division between the more public common area and the bedrooms. Since the primary function is flow, these spaces end up where they need to be as a byproduct of placing other rooms, and so aren't generally placed on their own. However, it is worth considering both the shape of the hall and the daylight in it. A dark hall will act as a bigger psychological barrier than a light one, but lack of light restricts the other uses of the space. A short straight hall isn't a big a psychological barrier as one with a bend in it, but always consider the easy of moving furniture.
Hallways are often considered a poor use of space, and many floor plans try to minimize them as much as possible. Another alternative is to widen them so they can also function as rooms. If instead of the standard three foot wide hall, you make a four foot wide hall you can put in a bookcase, or a pantry or other storage. If you widen it further, you can turn the extra space into a little alcove for bill paying, or if there is enough light, you can create a little alcove to read in.
Some rooms will have to allow for flow thru them, and so need to be sized to accommodate that. Knowing that people will want to take the shortest route (and so you can only get away with forcing a somewhat longer route without creating frustration), figure out what the flow pattern might be and make sure it doesn't interfere with the activity in the room.
Interior doors: The best place for a door is usually in the corner so it leaves most of the wall space available for furniture. Beware of positioning doors so they collide with other doors or prevent drawers from opening etc. Avoid putting doors at the end of hallways if the room is to be private, as privacy is gained by making it so you can't see into a room from another room.
When space to open door is limited, you can use double doors instead of a single door and this will cut the distance needed for the door swing in half. The downside is that double doors are not a standard item, so you will likely have to have them custom made. If you're making the double doors, consider making a non-standard thickness: they don't need to be as thick as a full size door, but if they're large enough, you might want them more like 1" or even 1-1/8" thick.
While code requires hallways be a minimum of 36" wide, standard interior doors are 30" wide, because most furniture is made to fit thru that size, although often barely. If there is a doorway near a bend in a hall, or in a central passageway, consider making the door 32" wide as that small amount of space will make moving furniture quite a bit easier. Since bathrooms generally have only built in fixtures, the door can be 28" instead, and occasionally they can be as small as 24". If there is a tub, make sure that in the future is can be replaced without having to tear the entire door opening apart.