Ever since I upgraded my Powerbook to 10.1, I've been experiencing a hang on boot-up when the OS indicates "Starting Directory Services". This delay has been as long as five minutes or more.
I wasn't getting this on my G4 tower, so I knew that it wasn't necessarily a 10.1 thing, but something that 10.1 brought out. I looked through my message logs (/var/log/message.log) and saw that lookupd was attempting to contact a lot of other machines and failing (lookupd is a software agent that acts as a network information broker).
I also remembered that I had been fooling around with lookupd, trying to set up an ad filter for web browsing and had added a directory called "locations" in my Netinfo database as part of that. I removed the directory using Netinfo Manager and now my Powerbook boots and shuts down quicker than it ever did, even in OS 9.
[Editor's note: This specific tip may not affect a lot of users, but the general tip is to make sure you check the log files to see what's happening to your machine, wether it's a startup stall or any other abnormal behavior.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2001100214325538