If you are considering taking a deep dive and striking out on your own, here are a few tips and tricks to get you started.
Take the time to write up a Professional Portfolio (PP). You can download my PP (in the document list on the right) from when I was dba (doing business as) Cornerstone Technologies Group from 1997 to 2001. It took many hours to write up these single paragraphs for all of my engagements, but a PP will give you credibility and help you to not forget what exactly it was that you worked so hard to accomplish through the years (!).
Your resume is separate from your PP, but should be included in printed packet you have at the ready to hand to clients. We all excel in different areas. If writing is not "your thing", evidenced by the fact that you cannot define an "object compliment" or "object of the preposition", hire someone to write your resume. There is no shame in this, only cash flow,
Keep samples of your work devoid of client proprietary information. When you are going it alone, you need to be able to prove your past accomplishments, not just speak about them. Sample work you should have at the ready are ERD diagrams, SSIS sample packages, SSRS reports and t-SQL scripts minimally. SharePoint screen prints, Visio diagrams and samples of documentation you have written is also helpful.
Understand that to bill 40 hours a week, you'll be putting in at least 45 hours with billing and sales pursuits. Time spent building and stabilizing your business is not billable, but it is necessary, so be prepared to work over-time.
Clearly identify to your clients the meaning of a billable hour. Here is an old Proverb for you: "God detests dishonest scales, but accurate weights find favor with him." Regardless of your religious beliefs, honesty pays great dividends and billable hours is an easy way to cheat. Find your personal integrity before you branch out on your own.
A good consultant will work themselves out of a job. Yes, that's right! If you are doing your job right, you'll be making your clients independent of you. It is your job to make your clients successful -- not to develop a life-long niche for yourself embedded forever into the wallboard of the IT server room. If you take this attitude from the start, you will never be out of a job as referrals will come spilling in faster than you can respond to them.
Here are a few basic forms that you will need (on the right). I've left them in Excel and Word format so you can easily download them and make them your own.