Of course, if the guy doesn't know what you're telling him, that's a different story, and in that case, there would be no 'as you know' part. That's a pretty well-known no-no, and it's been a long time since I've seen it.
Another one is the information dump. You might be writing along and suddenly you need to get something across to your reader, so you insert another character and tell him everything you think your reader needs to know. Take my word for it, your reader doesn't need to know all that information any sooner than anyone else, and if they do, it's time to back up and put it in the story where it belongs, even if that means adding in a new first chapter. Or you can simply allow your character to stumble upon the desired information as your story evolves.
And then there are some people who simply can't seem to find their tongue at all, falling back on the 'he told her' strategy. While this is a viable strategy to use occasionally, really, most of the time, we want to actually hear the words. Conversation is a unique opportunity for you to allow your reader to get to know your character. With each sentence, you can show your reader a little something about who is speaking.
Let's say one of your characters pulls her braid every time she gets nervous. It could be some little tell like this that would clue your reader into the fact that she's lying through her teeth. Or let's say you have a guy who polishes the toe of his shoe on the back of his pant-leg. This guy is always worried about how he looks to others. There's also the person who talks more with their hands than they do with words, gesturing when he can't come up with the right word.
There's other things you can put in there too. Walking, sitting, standing, groaning, sighing and the list goes on. It is important to keep your character in motion in one way or another, for a character that doesn't move = a story that doesn't progress.
One small thing that should be mentioned; variety in the tags - said, asked, and so on - do try to resist the urge. The purpose of tags is not to add flowers to the tabletop. The purpose is to forestall confusion, and if you pair action with dialog, very few tags are necessary.