There is probably not a great deal that needs to be done differently if you want to use a finished attic space as an office.

You will probably want to think very carefully about the weight of equipment, books, office supplies, etc. that will be in the room and err on the side of being extra careful about the adequacy of the structure to bear the extra weight.

You may also want to prewire for cable, wi-fi, DSL, etc. You might want to install extra electrical and phone outlets for easy connection to office machines.

Using the space as an office might argue for an exterior door if you have clients coming to your office. You also might want to consider a display area, bookshelves and storage carefully.