Does anyone have any tips on how to bring an over crowded forest back to health?

I have a section of pines, some birch, some maple, and cherry. Unfortunately they are so crowded that they have basically rendered the forest floor "dead". The bigger trees are not much good for timber (crooked or split). And clearly I need to open the place up a bit.

Its an old overgrown pasture, but the trees are at least 30-40 years old.

What should I look for when deciding who stays and who goes? How far apart should the remaining trees be from one another? [img]/forums/images/icons/confused.gif[/img]

The area in question is a 10 acre swath of land up here in Vermont.

Any insight would be greatly appreciated. [img]/forums/images/icons/laugh.gif[/img]