I use the free version of BackWPup as it allows me to back up the sites I manage to Dropbox in a straightforward way and for free. I tend to configure a daily database backup and weekly full site backups for all of my live sites.
A useful WordPress plugin to have installed as it automatically checks all hyperlinks used across a site and emails you if any are detected broken.
Many of my clients like to see a quick summary of their Google Analytics data in their WordPress dashboard. This is the best plugin I’ve found so far for doing that and I also like how it can be locked to connect to just one Google Analytics account/view.
I’ve tried out a few WordPress security plugins, but I keep coming back to WordFence. I find it provides suitable protection from hackers without being overwhelming with too many options. I now install it on all my websites.
My go-to WordPress SEO plugin as it also generates XML sitemaps, adds Open Graph meta data, Twitter card meta data as well, and Yoast is a highly respected WordPress developer.
ZenCache is my go-to caching plugin due to its ease of use and minimal configuration. I’m sure other WordPress caching plugins might perform better and offer more advanced features, but most of the time I find ZenCache is good enough.