Here are some areas to cover:
Order of operations (very important!)
Adding, subtracting, multiplying and dividing negative numbers and fractions
Adding, subtracting, multiplying and dividing algebraic expressions
Simplifying algebraic expressions
Solving simple, linear equations (respect the '=' sign!)
Finding the x and y intercepts of a linear equation
As for what to cover the first day, that entire list might be a bit much depending on what his problem areas are, but I'd start with the first two. If he's cruising through those, then you can jump to simplifying algebraic expressions. See if he's comfortable handling negative exponents in rational expressions.
I'm sure others can provide additional suggestions, but those should give you an idea of where he's at. He either has some really bad habits, doesn't understand the material, or both.