Don't take advice from people who want to give you advice.
Use the internet to find out everything you possibly can about your competition.
Use the internet to research the biographies of individuals who have been successful in the field of your new business.
To be successful in a business venture, you must have the equivalant of a PhD in the business side of the business. You have to know everything there is to know about how money is made in that business, and how money can be lost in it. You have to know who all the major players are, who the competition is, what they are doing, and how they screwed up. If they haven't screwed up, how are you going to break in? How is your idea better.
You have to know the history of the business, and how the industry (whatever industry it is) got into its present state. You have to understand this intimately, so that you can see how your business is going to fit into the bigger picture.
How will you know when you've learned enough?
You'll have learned enough when you can talk to someone else, someone who's been in that business a long time, and make them listen to you. And why will they take time out of your busy day to listen to you? Because you can teach them something they need to know.
The internet can help you do this. "Start up web forums" probably are useless.
“Don’t take advice from people who want to give you advice” is about the best advice I have ever seen. But now I am caught in a paradox!