I have used LaTeX for more than a decade, but still don't own a copy of the LaTeX Companion.
Update: I now do!
8 How to sort a .bib file with biber? sep 24
3 How to sort a .bib file with biber? dec 24
2 Can WhizzyTeX be used with XeTeX? dec 13 '12
2 How to use \autocite with biblatex-apa? mar 29 '13