Things to consider before running Update Statement

I will be updating a table in a single column. The update statement joins several table. Besides disabling the trigger before I execute this process, what else do I need to consider (Critical/Non-Critical?). Any suggestions?

What does that trigger normally do, and what is the reason for disabling it?
Can you take the database off-line, or can you schedule the update in down-time?
If it's critical data, you might consider copying all rows that you will update into an archive table, before running the update.