Jon Gilson from Again Faster and EC Syncowski explain how to maximize efficiency on the Concept 2 rower.
Concept 2 also has a couple of technique videos on their site.
Setting up and common mistakes.
- Leg drive, body swing, pull
- return stroke should take about twice as long as the out stroke
Another quick technique instruction with Olympian Erin Cafaro.
(Excerpts from here: Row with an Olympian Part1 / Part 2)
She says a 1 : 3 ratio for out stroke to return stroke is preferable.
Update: more rowing technique instructions.