Read this:
The Incomplete Secret Technique
Also:
More Snap I More Snap II
Also: The Beto vid above is essential.
Grab a stack of discs and go to a field. I like to use all similar mold and weight for this so that I can correct and modify my form with predictable results because all discs are essentially the same. At the very least, make sure they are all in the same class: all putters, all mids, or all drivers. There are dozens of threads about which discs are good for beginners; read around and decide for yourself what you want to use.
I recommend focusing on putters first. They are the easiest to control and the hardest to throw far. Also, you should switch your field disc selection up every so often--different classes of disc will help you improve different areas of your form. For example: putters are more sensitive to OAT, drivers more sensitive to nose angle.
Chuck those babies from a standstill until you can make them fly consistently flat and straight. Don't worry about distance at first, just flat and straight. After you have the discs flying flat and straight at your command, try to throw them flat and straight and a little farther. If you can do this, try to add even more distance, but take it in degrees. Always make sure you can control the direction of the disc before you throw it farther. If you lose control and discs start flying unpredictably, notch it down until you regain control, then push it out just a little farther.
Go home and read a few articles about technique. Watch the videos again. Think about what you learned while practicing, what you were probably doing wrong, and what you can incorporate next time.
Do it again. Start your session at flat and straight from a standstill. Slowly add more power, keeping it flat and straight while maintaining control. After a dozen iterations of this, you will have learned your limits and expanded them significantly. You will begin to recognize the feel of a good rip vs. the feel of a bad one.
When you feel comfortable with what you have at a standstill, you can start adding footwork at the end of your field sessions. From there you can move on to practicing various degrees of hyzer and anhyzer, but always remember to take it slow. Control is most important!