If you're not already well-versed: get familiar with Google Analytics, Google Tag Manager, Funnels, a/b Testing etc. It's cool to know other tools as well, but

If you're not already well-versed: get familiar with Google Analytics, Google Tag Manager, Funnels, a/b Testing etc. It's cool to know other tools as well, but privacy concerns or not, GA + GTM are the default. They're largely underused, but my experience is that clients love it when you can set it up for them, especially in combination with Adsense/Adwords to optimize their campaigns.