Remember good ergonomics also when you are using your smartphone – if using one is necessary at your work. Avoid looking down at your phone since hanging your head down will strain your neck.
Put your arm and shoulder muscles to work and lift your arm every time you need to look at your phone. If always holding your hand up is too strenuous, find something to rest your elbow on. For example a small pile of books!
And if your work includes a lot of phone calls, take full advantage of activating your days with them. Could you take some of your calls standing up and walk around the room as you speak? Or if you need to sit by the computer as you speak, why wouldn’t you quickly stand up and sit down every time your phone rings.