Penciling in
Merlin over at 43Folders gives his method of penciling in appointments in iCal - mine’s even more simple: A separate calendar/category for tentative appointments. When they become finalized, I just change the calendar that it exists in, and it’s now “penned” in.
Possibly Related
I do exactly the same thing - it seemed rather obvious really. I’ve also made the “unconfirmed” calendar a really garish magenta to force me to follow up.