So I try to make myself only look at the page and wave my mouse around. Usually that way I see whatever the developers/designers intended, because their intent is what everything else gets measured against. Then I check if keyboard can do what the mouse did, if the text sized larger are headings, if menus and widgets use the right, or a right, set of code, and maybe I'd use an automated tool to check for alt text if there are a lot of images. I eyeball what looks like poor contrast, look at the colours in devtools and plug them into Lea's analyser.