From a number of sources, I have got the following:
A deeper glove (my son's is 12") than a middle infielders. He's 10, 5' 1 1/2" and 135 lb.
Closed web pocket, such as a basket web (as opposed to say his 1B glove which has a single post and 2-crossbar design - can almost look through the web and see the ball when thrown or to get it out.
Cant be white or gray and if I understand correctly cant be two-tone in some leagues. My son's is the Rawling's pro-preferred taupe colour (sneaky devils).
The kip leather of the Pro-preferred models is, from what I understand, easier to break in that cowhide. My guy is pretty husky for a 10YO and his hands are pretty big. It would be a hard go for a more slightly-built player to work one of these in.
Careful with conditioners, etc. on a pitchers glove - that stuff comes off on balls, hands, etc. At season end, we use the Nokoma conditioner - it does not seem to add weight to the glove and restores the finish quite well.
Other gloves he liked were the older Easton Pro model which was all-leather and the Nokoma gloves.
D