How would you handle a player who wants to shoot an arrow and hide behind a tree. Can they move out of concealment, shoot an arrow, and move back into concealment?
A few ways:
a) Assuming it's a rogue or ranger, there are powers that allow movement before or after the attack. This allows you to move and attack
without breaking being hidden and gain combat advantage for the attack, and then still have a move action to use afterwards. I dont know if other classes that may be shootin' bows (archer bard, seeker) have such powers, however, off the top of my head.
b) If the character is on the edge of the obstruction, they still have concealment (so stay hidden) but can fire from around it (as they have an unobstructed corner). The act of firing breaks hidden, but they can still hide again afterwards using a move action, assuming they're legally able to be hidden where they are (or where they end up)
c) If you don't care about combat advantage, the use of an action point is possible as well, since you'd need two moves and a standard to go out, shoot, go back
d) As a continuation of c), if you can do one of the actions as a minor (eg, if you're a kobold and can shift as a minor, or if you happen to be a wizard with the power that lets you use magic missiles over and over) you can do it without an action point.