Although primarily an EMC Consultant, Henry Ott (before he retired) had a nice collection of tips on his website. Fortunately, archive.org had crawled his page

Although primarily an EMC Consultant, Henry Ott (before he retired) had a nice collection of tips on his website. Fortunately, archive.org had crawled his pages before they were taken down: https://web.archive.org/web/20160308031350/http://hottconsultants.com/ https://web.archive.org/web/20160308031350/http://hottconsul... (Bookmark this page, you WILL need it later if you do any serious EE stuff....) If you click on the "Tech Tips" link on the left side of that page, you will get to his discussion of multi-layer PCBs. ("PCB Stackup"). Read This Section, and Become Enlightened! ;-)