Always reading the dialog boxes is usually a very good idea, but I've also seen that strategy backfire.

Specifically, I was once trying to help a CS professor register a new domain name. This was at some low-cost registrar and there were 6 pages of upsells on the way to checkout. For whatever reason, he was definitely taking his time reading the entire pitch, and eventually I had to step in and click 'next' several times. "No, you don't need a new virus scanner as part of your domain name purchase. No you don't need a company to submit your new domain name to search engines. No you don't need SEO services. ..."