A lot of this is common sense, but I just witnessed an incident so here we go:
The people rooting through your bag, x-raying it, asking you questions and running sniffer-sensors round all your zips are doing it for your safety. They’re not nazis, they’re not idiots, they’re not bully-boys. They’re trying to stop the real idiots blowing you up. This is a good thing.
Don’t give them a hard time. Don’t make excuses. OK, you might forget and pack something you shouldn’t have. Mistake. It happens. Accept the fact that you’ll have to lose your nail scissors, large tube of toothpaste or authentic samurai sword with good grace and move on to immigration.
And for crying out loud don’t say that this is the first you’ve heard of it when you’ve walked past three huge signs on the way to the departure lounge, the restrictions were plastered all over the booking pages and flight confirmation sheets and it’s been in the news and enforced by the UK and US for several months – like one moron in the queue in front of me did.
The new regulations for international flights state that you may only carry gels, aerosols and fluids which come in containers no larger than 100ml/100g. In addition, all of these can come to a total of no more than 1l and must be kept in a clear plastic zip-lock bag (Darwin airport supplies these, I assume others do too). Note that, for example, if you have a 110g tube of toothpaste and it’s half-full, this is no good. The volume/capacity counted is the volume/capacity when full.
So if you want to keep your toothpaste in your carry-on luggage, ensure you buy a tube that’s 100g or smaller. Incidentally, in Oz at least, I found this very hard indeed. All the adult toothpastes started at 110g with very rare exception. Methinks someone needs to give the manufacturers the heads-up.