The biggest problem I see on existing fire jobs is that the paperwork was not kept up in the beginning, make sure to mark up all your prints with cable routes, splice points and detector addresses if using an addressable system. At the end of the job make a nice copy and leave it on site, it saves a lot of headaches further down the road. Fire work can be very simple if you take it one piece and one circuit at a time, when in doubt, rtfm.
