You need a valuation of your business; intimately know your numbers
Project how the business will perform going forwards (sales assumptions)
Understand what you need to do in order to get the business to the next milestone
Business defensibility (what stops others just copying you)
Know your competition
How big are they
What is their turnover
How mature are they (still growing?)
Know your product
Know your market/customers
Why will they buy your product
Evidence that potential customers like your product
How big is the market (in terms of $$$'s) and how much do you intend to take and how?
What are you going to do with the angel money?
Compelling reasons why you need extra investment
How is the investment going to generate a return for the investor?
At the end of the day the Angel is looking for a return on their investment. A chunky return. Be clear in your own mind how this will happen.
Why should they invest in me???
Investors, especially Angels, will invest in the person as much as the business. Make yourself as investable as possible. Knowing your stuff inside-out and having buckets of passion and a walk-thru-walls attitude is a great start.