Because lagers are fermented cold (50 degrees-ish), it's really important to make a large starter. A good resource for pitching is on mrmalty.com- there is a pitching calculator on there.
When I make lagers, I usually make the starter about four days in advance, then add another batch of cooled fresh wort the next day. This is called "stepping up" the starter. That is, I make a pint of water and 1/2 cup DME starter wort, cool it, and pitch it. I put some sanitized foil on the top, and shake it often. After a day, I do it again. Make another 1.040 starter wort (same amount- a pint of water to 1/2 cup DME), cool it, and add it. When that ferments out, I chill the wort. Two days later, I decant the spent wort (the yeast all falls to the bottom), and bring it up to 48 degrees by taking it out of the fridge about an hour before I want it. I then pitch the 48 degree yeast into 50 degree wort. That gives me a nice healthy start, as well as gets rid of that oxidized warm fermented beer from the starter.