I think the typical scope is 7:1, but most people go with ~5:1. I have 3 anchors on board, 2 8 lb fluke style and 1 13lb fluke style. My primary anchor is one of the 8lb with 15' chain and somewhere on the order of 150-200' of rode. I use the other 8lb anchor with no chain and around 100' of rode as a stern anchor. I don't use the 13lb one much and is more of a back up or if it's windy and need a second anchor off the bow. You can't go wrong with a couple sets of anchors properly setup for your boat, lake, bottom conditions. In my opinion a proper anchor setup is something you don't want to skimp on. Even mine is on the lighter side for chain/rode, but I always figure I can shackle some chain and more rode together if I need it. It's no fun with a dead engine or other mech failure and your anchor can't hold you from drifting.
West marine has some good info on anchoring
http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Anchoring-Techniques.htmEdit: I forgot a couple of items....for your shackles, go up 1 size from your chain as a rule of thumb. Also, use some zip ties for your shackle pins so you don't lose them in the lake. I actually zip tie my anchor directly to my chain and my chain direct to my rode too. Not sure if it will hold, but it's piece of mind that if I lose a shackle that I have a slim chance to recover my anchor. Of course that brings up the topic of having a recover line (not sure if that's the correct terminology) to pull up your anchor if it gets stuck too much. And finally, if you anchor in an area where people may drive across your anchor/rode, it doesn't hurt to have some marker buoys. I do this and still have almost had my anchor rode cut by some yahoo.