As Chris points out, in most applications these days you end up having to go with optimistic locking, which presents a few challenges. Chris works through the list of options. If you're building web/disconnected apps and need anything besides last update wins, this one is for you.
Quite a while back Andy wrote an article about why not using primary keys and clustered indexes was a worst practice. Chris weighs in this week with a great article that gives some more in depth info on clustered indexes and why he thinks they should be used on every table.