A basic skim of topics to have a firm grasp on before you start pre-calc would be;
-Points and Lines
-Perimeters, areas, and volumes of geometric figures.
-The Real Line
-Arithmetic between algebraic expresssions.
-Distributive law, factoring polynomials.
-Completing the square
-Radicals and Rationalization
-Trigonometric functions and inverse trig functions
-Graphs of trig functions
-Common values between trig functions
-Sine and Cosine laws.
Also, I would strongly recommend you are very very comfortable with function notation.
For a more comprehensive list, and even review, I'd recommend checking out http://media.wiley.com/product_data/...0764539841.pdf, if you can work through that, I'd say you are ready.