I do a ton of glade riding, actually unless the people I happen to be riding with can't do glades yet, its all I do. Things that really help me:
HELMET!! besides the obvious safety features being able to headbut branches is awesome
Quick turns to keep speed in control as snowolf mentioned,
Stop to scope your lines - unless its really shallow then try and make it through before stopping and having to hike out - (assuming theres decent amount of powder, anyways)
Once you decide on a line stick to it unless its something really dangerous, hesitating and changing your mind between one way or another often ends up hitting the tree in the middle.
Make sure your weight is positioned correctly, just about every fall / mistake I make in the trees is due to backseating, and then you don't have the control required to turn fast enough and keep under control.
Hope these help!