Here are my favorite TI-84 calculator tricks. Some of these tips you probably already know, but some might leave you scratching your head wondering why your Algebra teacher didn't show you how to do this.
Essential skills you need to know
Turn a decimal into a fraction
Enter a number or expression as a fraction
Make an x-y table and input any number for x
Find the intersection point(s) between two functions
Find the x-intercepts (a.k.a. zeros a.k.a. roots) of a function easily
Tips and tricks
Square root your previous answer
Enter a number using scientific notation
Reset the graph window to standard [-10, 10]
Access the built-in Periodic Table
More advanced skills
Use imaginary numbers
Open the F2 menu for quick access to absolute value, logs with different bases, calculus and statistics tools
Graph conic functions like circles, ellipses, hyperbolas, and parabolas
Quickly enter a matrix
Switch between radian and degree mode
Convert an angle from radians to degrees
Convert an angle to degrees, minutes, and seconds (and back)
Stay tuned for more posts on cool calculator tricks and other advanced topics, like how to use the STAT button, how to solve a system of equations on your calculator using matrices, and how to solve permutations and combinations problems.