Davide Giannella has been blogging for some time and has collected a nice set of Emacs tips going back to 2007. Mostly they are the solutions to problems that Giannella ran into and which we could probably figure out for ourselves but it’s nice to see them written out. Perhaps the list will help you remember a solution when you run across a similar problem.
If you use Emacs to deal with logs, you should take a look at his post about log4j-mode and log4j-start-filter. It seems like a useful tool. Thankfully, I don’t deal with log files much anymore so I haven’t tried it but you may find it useful. It’s still under active development and is available on Melpa.