What is the most common treatment for a dislocated collar bone?

Non-operative care. A collarbone (clavicle) can be dislocated both at the shoulder - an acromioclavicular dislocation ("separated shoulder") or much less commonly at the center of the chest (a sternoclavicular dislocation). The AC dislocation has six types, types 1-3 are the most common. Generally, treatment is conservative, with early motion and advancing activities as tolerated. Common rugby/footbal/hockey injury.
Sling. If you mean shoulder seperation sling or nothing rest activity restrictions.