You can sort buddies in the following ways:
Alphabetically: To sort buddies alphabetically, click the Buddy Name (A to Z) on the instant messenger pane. This button toggles every time you click it. To sort your buddies in the reverse order alphabetically, click Buddy Name (Z to A).
Based on their online status: To sort contacts based on their online status, click the downward arrow below the instant messenger toolbar.
Choose from the following options:
Show Online First: Select this option if you want the online buddies to appear first.
Show Offline First: Select this option if you want the offline buddies to appear first.