1. There’s a disclaimer on every page of this site for a reason. ALWAYS have a backup before starting any form of optimization. Some optimization techniques like cleaning a database are very hard to reverse, so if something breaks you’ll thank yourself for making a backup first.
2. Fewer things = fewer things to load = the page loads faster.
E.g.:
Fewer plugins = fewer files to load = the page loads faster.
Fewer images = fewer files to load = the page loads faster.
(Not a concrete rule though, which we’ll cover in the later post.)
3. There’s only so far you can go on bad hosting.
4. Test, test, test. Unless you use an identical setup (i.e. plugins, theme, and hosting) for every site, there are going to be different things you need to optimize. Use speed testing to find your weak points.