I am the approving authority (ergonomy/medical approval) for sit/stand workstation requests for a few thousand people, and have been making assessments on them for years. About 1/3 of people use them and love them. I have a prosthetic disc in my back, and that's the tip of the injury iceberg for me, and I prefer to sit. Standing is much harder, I can barely do 8 hours when called to. Anyway, there are two types of desk, one that you put on your existing desk and can raise/lower, and the other kind (favored by those who prefer standing over sitting) that raises the whole table up and down.
Just buy one that lets you place the monitor at or slightly below eye level, and rest you hands on the keyboard with your elbows at a 90 from your sides. That's it. I heartily recommend the anti-fatigue mat, it keeps circulation going and reduces fatigue. Obviously, get a desk that has springs or counterweights so it is effortless to adjust up and down.
Edit: Foot blocks also allow you to stretch while you stand.
Edit again: My wife is bananas over her walking desk. One of the guys in my office has a little office stair stepper he's always grinding on while working.