Steve, the first thing you need to do is develop some capital. Unfortunately, right now is a rough time to be going to banks for startup loans so if you have other means of raising funds you might want to explore those opitons. Depending on what kind of work you want to dive into off the bat, you will want to have at least one solid piece of equipment (skidsteer, excavator, loader) that meet your needs. If bank financing is hard you might check out one of the capital funding companies. They essentially buy the gear for you and you lease it back with a buy out option for a set period. It is a way to keep your cash liquid and still get the equipment you need.
Insurance is important. You will need general liability, inland marine (to cover your equipment) and workers compensation if you have employees. When I started on my own, I was doing site clearing/ excavation no lower that 8 inches and it was just me and a machine. I was able to get 5mil gl, 2mil wc and 2mil auto for around 2000/year. As you grow and add employees, and build more revenues those rate will go up.
As far as taxes go if you form an LLC (and pursuant to your state law) you have the option to be taxed as a corporation (money the company makes is taxed, then what you pay yourself is taxed at your personal rate) or as a pass through entity (you are taxed on the profits you make at your personal tax rate). Check with an attorney or cpa in your area to get the full details on what would work best for you.
As far as getting your foot in the door, I would suggest starting out doing some smaller jobs; maybe market yourself to a local construction contractor to do his demo on renovations. Look to align yourself with someone who does commercial and residential work to get a broad experience. You can also look in the legals section of your paper or subscribe to one of the monthly bid sheets. Check with your local AGC office, they can help you there. They can also advise you on licensing an permitting in your area.
I have been in the biz since birth really and the way to make the real money is to be your own boss. It's not easy but the rewards really are worth the time and effort.
Good luck on your planning!