This is my first instructable. (rate please :)) I'm going to teach you how to whistle loudly with your fingers! Then you will be able to whistle at baseball games, concerts, weddings, etc. or its just fun to piss off your friends. I will try to go in as much detail as I can. This is one of those things that you will get eventually if you try hard enough. Some people will get it immediately and some people will never get it. If you want more info there's probably a ton of it on the internet, I just didn't bother to check.
-Be aware that you are blowing air forcefully. It shouldn't take a lot of air to do the whistle when you've got it down, but when starting out never over-do it. At first you might feel dizzy, but I had a friend who kept trying and he eventually passed out. You should know when to you need to stop-
Step 1: Lips
The actual whistling sound isn't made with the lips. I see some people try it and they squeeze their lips together like a normal whistle. If you do that you'll just end up spitting all over the place. Lips stay relaxed, and curl over your teeth, so when you put your fingers in your mouth, they will not touch the teeth at all. Also, your lips should be wet.
Step 2: Fingers
There are different ways of doing this, the way I learned was to make a circle using your thumb and index finger. But there are other ways that might be easier for you.
Step 3: Tongue
The tongue is probably the hardest concept to describe. If you can roll your tongue into a tube, thats a good start. Basically, you want to curl the tip of your tongue up to the roof of your mouth. Your fingers will touch the underside tip of your tongue with all the arteries.