vagrant 

Vagrant is fantastic. It seems a lot more complicated than it is: basically there's a Mac app to install and then just a couple of command line commands and in the end you have a virtual server running on your computer that runs (among other things) a web site you're developing.

That means you can develop each project with the same version of languages, databases, etc that are on your production sites, and run a bunch of them at the same time. And when you version control your Vagrant configuration, other developers (like you, in the future, wondering what you did before) can get up and running right away.

Basically you need VirtualBox 4 — https://www.virtualbox.org/wiki/Download_Old_Builds_4_3

…then Vagrant — https://vagrantup.com/downloads.html

And this little menu bar utility can help you avoid the command line, if you prefer: https://www.github.com/BipSync/VagrantBar