Tara showed us two different ways to achieve that wonderful lettuce/rolled hem that is often used as a hemming alternate.

Serger lettuce hem:
Left needle only
Knife on
Needle tension at 4
Both looper tensions at 5
Thread length at R for rolled hem
These are settings on my Janome8004D 

Sewing Machine Lettuce Hem:
Zig zag stitch
Tension on +1
Stitch length set to 1
Stitch width set to 4 or 5
Settings on my Singer Confidence

Watch my live demonstration of the rolled hems techniques I prefer.