Having recently flown to Italy and back from LA, I had two different international first class experiences. Also note that domestic first class can be a different configuration as well. Sometimes the airline's website will show pictures and have descriptions of the first class accommodations as well.
New York to London: "Business Class" (there was a "first class" section for even more $$)
Three columns, single seats on outer columns and two seats in the center. The seats were more like pods, having a more private feel to them. My husband was sitting next to me (we were in the center column) and I couldn't see him unless I leaned over and looked into his pod. We were separated by a partition near our heads, but the rest was mostly open to his side.
Each pod has a personal screen with touch and remote options. There were tons of movies available for free, as well as some music and TV shows. Our seats reclined completely into beds, allowing us to adjusting our seats into any position we wanted in between. There was tons of storage, noise canceling headphones were offered free of charge to borrow during the flight, and pillows/blankets were also in our pods.
We were given a menu with three entree options, including steak, fish, and chicken. There was an appetizer and desert also included. The little silverware and salt/pepper shakers they give you are adorable and tiny! (if you're into that sort of thing)
They offered water, champagne, or orange juice before the plane even took off. Drinks after that are unlimited. The flight staff is very friendly and they will even know your name (via their seating chart)!
London to New York: First Class (this plane had no distinctions between business and first)
Three columns, two seats on outer columns and three seats in the center. These seats were large and could recline to an almost flat position. The cabin was open, just like in coach, so no privacy like before in the pods. The food and drink situation was the same, as was the personal screen at each seat. The configuration and privacy level were the main differences.
Domestic First Class:
This is very similar to the London to New York flight, except the planes are usually smaller, so the number of seats in each column will be fewer. These flights are also shorter in duration, so meals aren't always served. If they are, you do get options, and if they aren't, you still get to drink as much as you want for free and you get a nice snack. The noise-cancelling headphones aren't available and the seats never recline anywhere near a bed position. They are still oversized and offer you a pillow/blanket.
I hope this helps! My husband flies all the time for work in first class, so if you need any other details, just ask!