fill factor guestimate

Hi,

I have a table that will be updated frequently. Each row will be
updated at least once during it's lifetime, and most rows will be
updated ~10 times in their first 2 weeks of existence, and then
relatively rarely after that. The rows are being updated by a prepared
statement that gets executed with ~100 - ~600 different parameter
sets, each one updating a single row. What should my initial
best-guess fill-factor for the table be? Most of the updates don't
touch an indexed column, so I'm hoping to take advantage of the HOT
update feature. Will EXPLAIN tell me if an UPDATE uses HOT?

thanks
-Dave