to Mustang Evolution
Many members here use Meguire's products and swear by them. Recently I used Surf City's Voodoo Blend Rejuvantor and was pretty happy with the results. It gave my seats a dark shine without that greasy feel and the stuff does smell pretty great (leather).
As for taking care of them, just wipre them down with regular car washers. I'd say every three months just take a wipe cloth and wipe them down (assuming you wash your car every three months). Protectant should be use once or twice a year usually.
Best bet is to check the back of the product you are using and see their recommendations for it. Some companies differ with their products.
I'm sure SpectorV and PureVenom will chime in and give better advice on when to maintain them - those guys, so I've heard, are crazy about keeping their cars clean.