10,000 years and counting...they must be good, right?  And they're an absolute POWERHOUSE of nutrition!  Lentils contain the highest protein content of any vegetable other than soybeans (negligably higher)...fat free...cholesterol free...higher in folate than any other non-fortified food...and a really good source of iron (make sure you eat the lentils with Vitamin C foods so you get maximum absorbtion of the iron: tomatoes, green bell peppers, etc).Simmer (bubbles JUST breaking the surface - I call it "smiling") your lentils without salt - as salt toughens the skin.  Add the salt at the end to taste.  One part lentils to 3 parts liquid is a good place to start if you want maximum absorption.  The Red Chief tends to be my favorite, as it gets mushy and I like to puree it for a "fine" soup, but beware, they turn yellow, they are not red after they're cooked!  Golden Lentils cook more quickly if you're short on time.  French green lentils (Lentille du Puy) contain less starch so they're firmer when they're  cooked.  Brown lentils are cheap and easy to find.  They take alot longer to cook though - around 45 minutes because they have tougher skins.  These days, though, you can find multiple varieties of lentils in almost any grocery store!!