400 Freestyle advice?

I've traditionally been more of a sprinter, but I've decided to give the 400 free a try next weekend. I'm interested in ideas of how I should pace the race since I just have some vague thoughts on how to do this (e.g cruise the first 200, then slightly decend the last 2 100s). But I really don't what pace I can sustain for 5min, and I'd rather not have any pianos falling. I haven't done any testing regarding this, but I'm pretty familiar with sendoffs that I can make in practice. I also have 50-100-200 times that may give some perspective- I suppose it depends on the individual to a large degree, but is there some general rule that can be applied (e.g your first 200 should be your best 200 time +10sec) based on your times from shorter races, or should I be looking at this differently? Thanks in advance.