I was given a piece of knowledge that may prove useful and it has proved correct on several occasions.

If you are able to choose who you go to...be it an immigration officer or a customs officer...always choose the oldest ones.

The younger ones have everything to prove to their bosses and are keen to make an impression.The older ones couldn't give a toss as they are relatively senior in their role and don't have anything to prove.

The older ones in my experience won't interrogate as much, if at all.