I find it easiest when I do an outline for my books. Even if it's a basic one that just follows the three acts. But generally I do a breakdown of each chapter and what will happen in it. Later on I don't have to necessarily stick to everything in the outline if something comes up, but it gives me a guideline so I don't ramble on.
The other thing that is important is that you make time to write every day. Even if you sit in front of your screen and only one or two words work by the end, it's progress. Like anything else, until you start doing it daily, your mind doesn't get in the habit of creating daily.
There are some great writer's forums out there and they will give you feedback on your work. Absolute Writers has a great forum for that. They also have lots of tips and advice for writers.
Also, there is a free event you might be interested in. It takes place every November. It's called National Novel Writing Month (NaNoWriMo). You can sign up for it and there are loads of writers there who all try to write 50,000 words in the month of November. It's an absolute blast!
I know I'm coming up to this late, but I hope some of these tips help.