Excel

Excel is a great program that I'm sure everyone has made at least one graph with. Other than just making nice charts and graphs, excel has a metric boat load of commands and functions that are super useful. As a reference, the more functions you know, the more time you'll be able to save with a wide assortment of tasks that involve calculations.

I highly recommend taking a bit of time to learn more about excel (and any other programs you might be using at the moment).

Excel isn't something you'll be able to master in a week. There are literally hundreds of functions available to use.

For anyone who doesn't have Excel, I'm sure there's a way for you to acquire it somehow.

There are also probably free programs that have similar functions out there but I haven't tested any of them.