One of the first sweeps I have learned.
Considering the times I have tried this sweep and failed, the disturbance of your opponents base seems to be critical.
Grip one side arm of your opponent and same side collar
Open guard and scoot hips to bring knee across opponents waist/chest
Bring opponent toward you to disturb base of support.
Look over shoulder as your scissor your legs. Knee shield leg moves toward floor.
Kurt Osiander explains this better in the video.