Here is the site that helped me learn to fly cast. Flycasting Tips - The Basic Cast
The cracking like a whip comes from starting your next stroke to soon. You are not giving it the leader enough time to straighten out all the way. The problem with the line forming a mess on the water comes from not enough power or complete stop of the forward cast.

As mentioned a beginners casting video will help but not necessary. If you take half of your fly rod and a long piece of yarn(10 to 15 feet), you can use this to pratice casting indoors. Just string yarn through the upper half of your fly rod and use about 5 to 8 ft of yarn at first. As your casting improves you can use a longer length of yarn. You can also set out plates to help your accuracy. Just scatter them around and practice casting to them with the yarn set up.

When you get ready to try casting your complete fly rod and line use a small peice of yarn on the end and pratice in a feild or your yard. This way if you do break off you are not losing any flies. It is also easy to cast lighter flies than heavier ones so start. Heavier flies will reguire a little more power in your stroke which will making your timing a little differnt. Also dont forget to come to a complete stop on your foward and backcast. You do not want it to be a countinouse motion.