Do you have a plan drawing?
Have you check materiel pricing?
New two story/one? Small room or whole house add on?
New slab floor/wood floor?
Are you adding on to back or side to in large a room or rooms? Is the old wall a baring wall that you are adding onto?
Do you want open trusses or closed?
Is there going to be plumbing?
Are you doing footer yourself?
Is your old electric panel capable of handling more circuits and well you be doing the wiring?
What parts well you be contracting out?
I added a12x24 11 years ago. Single story slab floor and it was no big deal (contracted for floor and footer) did the rest myself. I did not tear down any of the old just added to the back of it and took out a window to make it a door way from old to new bedroom and back door (old doorway) to eating and laundry room with new back door.
This year working on a 22x24 second floor 4rooms. Closed in now but doing the siding/wiring/plumbing/drywall/floors.
All this was easy for me but keep in mind I have been doing this for a number of years.
Books and tapes can help but cant answer questions when you have a problem and sometimes you dont have the time to wait till you get answers. But if you want some reading and shows to look at try going to the Home Time site and TV programming guide.