How to create a sticker type effect

The Offset Path command works well. I'll usually make a copy of the object (and maybe move it to a layer underneath the original object), use the Pathfinder Unite command to weld everything together and then apply the Offset Path command to it. The numerical entry lets you dictate how big the offset (or "outline") effect will be outside the original art. Negative numbers let you offset inside the path. Corner settings will let you create sharp or rounded corners on the path effect. The effect is live and can be adjusted. Use the expand appearance command to make the effect permanent.