If you simply need to perform a calculation, you can use the Formula bar as a calculator.

You can use Excel's AutoCorrect feature to create shortcuts for commonly used words or phrases.

If you would like to better understand how some of these complex array formulas work, consider using a handy tool - Formula Evaluator:

Solver tool allows you to specify multiple adjustable cells and constraints on the values that the adjustable cells can have, generate a solution that maximizes or minimizes a particular worksheet cell, generate multiple solutions to a problem.

Sometimes it is handy to view (and print) the formulas in all the cells in a spreadsheet with out having to manually enter each cell.