MOVE OUT OF THE DAMN FIRE NOOB!
This is what most hunters think of when you mention "positioning", and yes, not standing in fire is very important, but there is a much more subtle meaning to the term, one which top hunters know and allows you to truly maximize your DPS.
When it comes to setting yourself up for a boss fight, there are a couple of questions you have to ask yourself:
Are the things that make me move predictable? (ie: is the position the pop up on preset, like Ragnaros' Sulphuras Smash or random like Magma Traps)
If they are predictable, are they static or mobile?
The main goal is to try and keep out of Aspect of the Fox for as long as possible by keeping your movement to a minimum, and this is what the first question is for. Most abilities are predictable in knowing when they're going to be cast but not all are positioned in a constant way. For the unpredictable, bite the bullet and hope it is in between casts so you aren't interrupting one. The predictable static ones though, here's a hint: stand on the edge. A good example is Valonia's Deep Breathe (DB) in the BOT V&T fight. This is a good example of predictable events and where to stand. Near the wall, not good, it's easy to get caught too far in and then breathed on. Find a spot near the edge of the flames that would be thrown down in the center ( either side will do) and wait. If you are closer to the entrance here's what will happen. DB on entrance, step 1 or 2 steps forward, Center, 1 or 2 back, and exit, no worries. If you watch videos of boss encounters you will see that most ground effects that are predictable and have a sweet spot to stand in that will require very little movement on your part.
Other things to consider are do we have to stack or spread? Where are my healers? Am I close enough to launch my traps as needed? The trick to these questions are look to see where you are at the START of the fight and what the group as a whole are going to do during the encounter. Once you learn how to read raid groups quickly, positioning will come quickly and naturally.
Some tips for when you have to move.:
Macro in your Aspect of the Hawk to your signature shot (ie Chimera),arcane, and serpent sting because these are all shots that don't need AotF to fire on the move.
When you know you have to move, try and time it so you don't have to switch aspect at all and you can keep up ISS (if you're a MM)
Finally, make sure you're pointed in the right direction if you have to move.
Good luck and I hope this helps improve your game. :)