With NoScript, I started off with everything blocked, and just stuck the extension icon into the toolbar. Whenever a site wouldn't load properly, I'd temporarily enable the JS just for that single domain, and see if that got it to work. If it didn't, I would usually poke about and see what other domains need to be unblocked. It's pretty common that you might need to unblock some CDN or a 'static' subdomain to get the site to load. If it's a website I expect to come back to, I will then switch those exemptions to permanent, but otherwise I try to avoid leaving a lot of cruft in the whitelist.