Scraping best practices, download the source code and select an element with Jsoup?

I want to scrape a page using Java, PhantomJS and Selenium. I assume (and please correct me if I'm wrong), if I want to scrape a page and not create allot of calls, than I should probably get the html to a string (or a file) and use Jsoup (or any other library) to extract the relevant information.

What is the best practice (resource wise) to select an element with Jsoup?

Thanks allot,