Tender, moist Meatloaf?

I've always added a half cup or so of sour cream and an egg, along with the breadcrumbs and sautéed onions.

One trick I've been using. And it's a keeper. Is Cooks Illustrated tip of adding a 1/2 tsp of unflavored gelatin to 1/2 cup of stock..and let it bloom a bit.
Add that to the bread crumb mix
If you aren't using higher fat pork in the meat mix..and using an all beef meatloaf.
The gelatin replaces and holds the moisture in you'd get from the pork/veal additions.
http://whatdidyoueat.typepad.com/what_did_you_eat/2006/12/a_few_weeks_ago.html

I will try Oscar Night and Mom's Meatloaf, first. the more traditional the better. thanks!

You need meat that's at least 20% fat, sauteed aromatics such as onions and garlic, and a minimal amount of breadcrumbs. Don't overmix it--mix it just till everything is blended together. And bake it at a fairly low temperature (around 325) till the internal temperature is 155-160--which could take almost an hour--but that way the meatloaf won't be dry. Here are the Food52 meatloaf recipes: http://www.food52.com/recipes/search?recipe_search=meatloaf

(I highly recommend the blackberry barbecue sauce.)