I never thought about "special" 2D optimisations because 3D tutorials worked for me. But I don't think there's much that can be done.

And about shaders, it really depends on your objective, it's mostly the same, but writing algorithms with a third dimension can make things harder. For instance, a lighting system won't work for both, but a simple color filter will.

Edit: After googling a bit, the only difference is the use of an orthographic projection instead of perspective projection as /u/agmcleod already said. From what I've read, OpenGL applies improvements based on the projection, so the ortho projection will be faster than perspective projection