Key promoter is a plugin that I have been using a while now, and it has proven it's benefits. Easy, small and making itself useless in time, Key promoter is a quick way to learn which combination of keys enable which functionalities in IntelliJ. Creating your own shortcuts is encourraged and super easy.
As only non-mac-developer here @work the plugin reminds me which shortcuts to use on the macbooks, saves me a lot of time during pairprogramming.
Summary: Install it, love it.