Hi
There is a Business checklist on
www.business.govt.au 
I am starting my own business the main things that you really need to do are..
1/ Business Plan - This is most important
2/ Knowing your personal short-term and long term GOALS!!!
3/ Business objectives
4/ S.W.O.T - Strengths, Weaknesses, Opportunities and Threats... Don't be modest be realistic...
5/ Marketing - Research your Point of Difference, Competitors, Target Market, Prices others are charging - Measure your client base, profit average, growth - Execute, Just do it - HAVE A MARKETING PLAN
6/ Construct a Survey on your business and get at least 100 random people to take it
7/ Know what type of business you will be best suited to eg; sole trader etc
8/ Have at least 2-3 contingency plans - cover your back you never know what can happen to you.
9/ Be realistic in your cashflow budgets, overhead costs, Direct Cost of Sales and work out your break-even amount how much you need to sell of your product or service to cover your Business and Personal expenses.
Pretty much it is alot of research and effort that goes into a business plan but it is well worth it to know if it is going to work.
Marketing is the main at least 40-50% of your business plan should be focused on how you are going to attract your clients base and then maintain the clients and lastly keep growing your client base marketing is never ending.
I really hope this helps you and good luck in your business venture.
Sincerely
If you need help with your plan private message me... I am happy to help with what I can