I usually write, say, "Cleric 5 (Bob)/Ranger 3 ... HD 8d8+8; 46 hp" when I'm doing formal stat blocks.
In my personal notes, lately I've been writing, e.g. "Cleric 5 (Cthulhu)/Ranger 3 ... HP 46 (8 HD)" just as a quick jot. Of course, I've seen that format in the DMG II and in Dragon, so that's kind of influencing my personal notes right now.
I used to abbreviate the classes (Clr5(Fnord)/Rgr3), but some just don't have an intuitive abbreviation (Knight Protector of the Great Kingdom, I'm looking at you!).
TWK
Not that Bob and Cthulhu are all that willing to grant spells....