When seated, stand up every 30 minutes and stretch your shoulder blades back

Consider a sit/stand desk with a comfort mat for the feet

Avoid “Text Neck” by bringing your phone/tablet up towards chest level rather than hunching forward

Use chair with armrests

Use lumbar cushion on chair to support lower back

Sit upright on your sitting bones to maintain the arch in the lower back if your chair does not have a lumbar support

Have screen in front of you at eye level

Use keyboard tray wide enough to include mouse

Keep phone close to you

Do not cradle phone between shoulder and ear

Use a phone headset

See this document: Workstation Ergonomics – Checklist