Tip 01: Don't Leave Luggage Unattended
Apart from the obvious security worries leaving your luggage lying around can cause, do you really want it nicked? That confidential document from the office, that £100 pair of designer jeans, that cuddly toy for your nephew Billy, or even those more-than-slightly-embarrassing holiday photos that you have just had developed? Do you want any of that lot stolen? Pilfered? Removed from your possession? (Or in the case of the photos, put on the Internet?)
So don't leave it unattended in a public place! Sit with your luggage. Place it on your knee. If it's too big, then stand with it. Hell, sit on it if you want. Just don't leave it alone.
While we are on the subject of luggage: Don't watch a stranger's luggage for them either.
"Would you just watch this for me...?"
There is nowhere on a station or platform that people can go and cannot take their own luggage with them: it would defeat the purpose of stations and platforms.