Some posts on doing mathematics starting in Algebra 1. There are a few that reference calculus, but these, I hope, will help pre-calculus students get off to a good start and not have to unlearn things later.
Teaching How to Read Mathematics Hints and suggestions
A Note on Notation Why I like using parentheses for sin(x)
Why Radians Some calculus here after the first three paragraphs.
Stamp Out Slope-intercept Form! There is a much easier and understandable way to write the equation of a line.
How to Tell your Asymptote from a Hole in the Graph Calculator hints for seeing discontinuities.
Testing, but NOT for Calculus Understanding false positive and false negative results for medical testing.
Quadratic Formula or not? A new approach to an old problem.
Amortization Find your monthly payment of a loan. – An application of finite geometric series (no calculus)