Newbie Race Advice Wanted

Ok, I am doing my first ever multi-sport event on Sunday.  It is a duathlon: 5k run - 32k bike - 5k run.  I am looking for advice for a first time multi-sport racer.  I have a running background, so I know what to expect as far as pre-race prep for hydration, nutrition, etc. 

Any advice would be appreciated for transitions (no clipless pedals), and the bike portion of the race (I've never biked in a large group). 

One other stupid newbie question - do I pin the race number to my jersey or do something different for bike and run?

Any other lessons for a first timer?  Thanks for your patience and advice!