I'm wondering if any of the stronger players on this forum would be willing to write a brief introduction to the contrast of the different opening corner plays. I've played the start points for a long time and have only recently been experimenting with the 3x4s. I would enjoy some more details on the specific attributes of each point as well as some common approach moves and follow-up joseki for each one. For instance, I know that the start points are intended to be attacking stones and like to expand along the sides and are weak in regard to controlling the corner. I'm looking for more of this kind of theory for all the basic corner positions. Even at my level, I see some people play 5x4s and 5x3s and what not but know nothing about their particular strengths and weaknesses. If someone would be so kind, I think that the community here would greatly appreciate it.

On a rather separate note, I occasionally see pro games where the game will not open in the standard fashion of taking the four corners with the first four moves. Instead, one player (usually white) will make an approach move or a side extension while one corner still remains vacant. Could someone give insight as to why one would pass on the first move advantage in a corner and what sort of position call for such play?

Here is an example of one such game. I am unable to download the sgf and you'll need an account to view it.

http://www.go4go.net/go/games/sgfview/14461

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Thinking like a go player during a game of chess is like bringing a knife to a gun-fight. Thinking like a chess player during a game of go feels like getting knifed while you're holding a gun...

You might find some insight in Peter Mioch's gentle joseki series, found here:
http://gobase.org/studying/articles/mioch/

There's some info on Sensei's library regarding first move choice as well that may be helpful.

Edit:
Charles Matthews' On Your Side series may also be good:
http://gobase.org/studying/articles/matthews/fuseki/

The book In the Beginning by Ishigure, published by Kiseido, starts off with a long discussion (pp. 7 -18) of just what you asked for.

Yilun Yang's book 'Fundamental principles of Go' has a chapter of exactly that.

As for early approaches, although there are some situations they are better than taking an empty corner (such as facing 3-4s), often it is part psychological, white wants to get in Black's face, take the initiative and not get bossed around. It stops Black making his favourite fuseki and gets out of the opening book earlier.

A great book.

While it's probably too difficult in general for a beginner "The Direction of Play" goes into more detail about the meaning of the opening moves: 4-4, 3-3, 3-4, 5-3, etc.