I used to go to the post office for a book of stamps like everyone else, but last time I order them online and there here was a small handling fee. It surprised me though that it took a week to get them. It isn't handled by the local office but by a central facility out west.
I don't have delivery at the house because my box kept being destroyed by snow plodwsand other assorted people. Is when I get my mail from my PO Box I just buy more stamps when I need them which is not that often.
All stamps are now "forever" stamps. The printed value will remain valid forever. Stock up on as many as you can afford. I guess it probably depends on your situation, and I know there is an official order form for stamps, in my rural zip code I just leave cash and a note in my mailbox. When I was a carrier, I would often circumvent the "proper" procedure and do the same. Get to know your letter carrier,there is service and then there is better service. Right or wrong I was always more willing to go the extra step for Joe and Matilda who would speak to me,give me a cold drink,etc, than I was for 294 W Park St. who I seldom saw and when I did they didn't speak.
I buy a lot of stamps. Although I pay most bills online, I belong to a book and movie swap club, so I mail out a lot of books. I buy the stamps online too, so it minimizes the time I have to spend in the Post Office.