The wind window is an important thing to understand. To become familiar with the wind and being able to determine where it is strongest and where it is lighter. Obviously, as you fly your kite through the window the flight speed and characteristics can change. With the wind at your back (yep, have to say it - n'uff said ;)) you will find the power zone directly in front of you. You will find your kite is fast and pulls the hardest in this area.
As the kite approaches the zenith or the top of the window the kite will slow down and generate less power.
As you fly to the outer edges of the window, left and right sides, the speed and power will diminish also.
In higher wind days, I will often launch and land towards the outer edge of the window. This allows for a slower, more controlled launch or landing. I also tend to trick there on the higher wind days - I try and find the sweet spot where I can get enough wind at the right speed to play.
Be aware of what is up wind from you. Trees and buildings can have a dramatic impact on the wind quality. The air moving through trees or around building can make for some trashy wind as opposed to smooth and steady. Trashy wind buffets the sail and doesn't fill or stay filled properly and this affects flight. Hills and valleys can also produce some interesting wind that rolls. Personally, my favorite wind is ocean wind - smooooooth - but as a land-locked prairie boy you learn to take what you can get!
While we are talking about being aware, check for overhead power lines - flying into power lines is a recipe for a really bad day! It can kill ya and vaporize your kite in short order. Ben Franklin flying his kite with a key makes for a cute story but flying kites in a lightning storm is a special kind of stupid! Seriously though, please fly safe, we want kites to be a fun healthy activity for you!
Two last things. Watch out for people. Stunt kites and foils can get going pretty fast and sometimes people don't see or think about the lines. Kite lines under load with speed can really hurt someone. Be aware other others using the space.
Last thing... DOGS. I have had several flyers share stories of how a dog playfully attacked their kite and caused significant damage. I know... dogs are supposed to be on a leash and the owners are responsible for them but I have yet to see a dog owner compensate a flyer for a DDK (Dog Destroyed Kite).
Fly safe, have fun and smooth winds!