All of the above is great advice and I only want to emphasize that to be consistently successful walleye fishing you need to be in contact with the bottom whether its in 10 feet or 30 feet. Keep whatever lure you are using within 3 feet of the bottom and make sure that you can easily touch the bottom with your lure at all times by just dropping your rod down when jigging or back when trolling.
Most beginners are very reluctant to do this because they are afraid of snags and losing lures. It does happen but there are some tricks to preventing snags and losing lures.
That's a topic for another post!