The actual starting point for hanging doors is knowing the sizes you will need and which way these doors will swing.
A majority of the time interior doors will swing into a room. Some times there are circumstances where a door will swing outward and that may be a situation where there is not enough room for the door to swing inward. A small closet with a swinging interior door might be an example.
Right Hand or Left hand Swing?
To easily find out which way the door swings is by walking into a room and looking at which side the light switch is on. If the light switch is on the right hand side as you walk in to a room, this would be a left hand swing door. If you walk into a room and the light switch is on the left side then this would be a right hand swing door. Both of these examples are where the door swings into a room.
The Size Of the Door For The Opening
To figure out the size of interior swinging door you need for each opening is also very easy. A roughed frame opening is usually framed 2" inches bigger then the size of the actual door.
For example a bedroom door is normally a 2'- 6" door. A 2'- 6" door equals 30" inches so the framed opening would be 32"inches wide. A bathroom door is normally a 2' - 4" door and this equals a 28"inch door so the framed opening will be framed at 30"inches.
These examples of sizes of doors are not always the case in every single home but are a standard in today's building. An example where this may not be the case is a handicap accessible home and in this situation the doors may all be 3'- 0". Another example is the older homes; some times they have bigger or different sizes.
Now you should have a good understanding of how to figure out the sizes of doors you will need and also the swing of each door. There are installation instructions for hanging interior doors at this page installing interior doors .
There are some important points to keep in mind when hanging your doors.
One is the type of flooring that will be installed or is already installed. If carpeting is being installed later the door will need to be held up slightly so the swing of the door does not drag on the carpeting.
Before hanging doors it is worth reading how the doors are hung for some critical points and to be sure the door will operate properly. This will also give you a good understanding of how doors work for later adjustments from years of use.