I’ve used the resources on Utah Mountain Biking to get good instructions. Even though they’re called Utah Mountain Biking, much of their advice applies to road bikes as well.
Other than that, I tend to just Google the repair I need to do. Someone usually has good instructions. Try “clean chain bike”, “replace derailleur cable”, and “clean bike”.
Another good resource is the website of your parts manufacturer: often, with higher-end components, you’ll be able to look up manuals for service on each part. For example, I looked up the manual for my disc brakes and I got good information on how to replace brake pads, tighten cables, and adjust brakes. Often, these are PDFs, so you can download them and/or print them nicely if you like.