So you want to go fast aye? Really fast? Planing is one of those things in life that you need to experience on your own to know what it feels like. No matter how much you read up on it, you need to break the barrier yourself. Planing is pretty much like slipping on ice, you are skipping on water with only a small surface of the board. It feels like warp speed on your first time and the acceleration is awesome. Don't let that scare you, windsurfers always come back with a huge smile totally hooked for life, and it stays that way. This is also one of the reason windsurfers don't feel the need to progress beyond this point, because it's just so darn fun. Many are happy just planing for the rest of their windsurfing lives. With a few skills up your sleeve you'll be planing in no time, and these are the skills you need.
Wind, you need at least 15 to 20 knots of wind to ensure you don't have to pump yourself to get planing. With the right technique, you should be planing comfortably in these winds. You also need to know how to use a harness and know how to get into the foot straps. If you can do that, the rest is easy. Some folk encourage people to experience planing without the harness, but its not the full experience and it also gets tiring on the arms. From my point of view, it's not half as enjoyable as it is hooked in. So although you can get this done without the harness, I encourage you to first get the hang of harness use and then try for planing, but its your call. In my first experience I got planing in the foot straps without the harness and while planing I managed to hook in, and wow what a difference!
Once you are strapped and hooked in you need to make sure that you are in control before you take off and skip away. To be in control you need to use your back hand by sheeting out slightly with your back leg bent, your weight needs to be in the harness and your front foot should be used as pressure against the sail.
When you feel steady and in control, sheet in, lean back and keep your weight in the harness. Your body needs to be light on the board and at the same time your weight must be on the back of your board. With these two combinations you'll start to take off. Your board will start to shimmer with some spray, but this is not planing yet, lets call this pre-planing. The board and sail will feel full with power and like it wants to take off, with your weight off the board it will do just that, take off. You'll feel a sudden release and this is planing. Now that you are planing that's not the end of it. Relax your arms and let your hips do the talking, don't over sheet. Move your body around to find that spot which feels comfortable and powerful. Remember if you are not totally comfortable something is not right, recheck your body position and gear!
Check the position of your mast track on the board in relation to the conditions and also make sure your board and sail is not too big or small for the wind.
On your first go take a look at the other sailors and see what sizes they are using, don't feel shy to ask. See what the bigger guys have got rigged up versus the smaller guys. This will give you a good head start on what to go out with for your very first planing experience! Rip it up!