In your suitcase (not hand luggage)
Valve off (if you can) if not remove burst disk
Barrel off (believe me people do do it!!)
Batteries out of hopper
Batteries out of timer
Batteries out of goggle fan (if you have one)
Copy of PGI on top of all the clothes
TELL THEM WHAT YOU HAVE !!!!! and don't let the case out of your sight...you will get escorted to security and they will either x-ray or actually search it....not an issue either way you then get your cases treated on an individual basis....(they don't weigh them btw

ssssh )
I have been flying before and fools within the team 'cos they had lots of dvd's etc in thier case tried to just check in
normally.......didn't work !! The UK is really cool about things going out its the other end it gets a little awkward with brain dead check-in staff not know what can and can't be carried...was told my air tank couldn't fly (it was empty and no valve) and it was the same airline I had flown into the country with !! But then as I have done this a few times the check-in fool was soon put right.
The phone ahead part is fine in principle but you can be sure that the person that said it was fine will not be available when you check-in (have done it that way and as above and never been refused to leave this country yet !!) Insurrance is an issue you will need to check with your household insurrance people cos your travel insurrance will NOT cover the amount your marker is worth and chances are neither will your home insurrance cos of the value of a marker is so high that you would "generally have to specify the item on the household policy