Mobile phones are oftern stolen, so here's a tip
To check your mobile phone's serial number, key in the following sequence into your phone: * # 0 6 #
A 15 digit code will appear on your screen. This number is unique to your handset. Write it down and keep it safe. Should your phone get stolen, you can phone your service provider and give them this code. They will then be able to block your handset so even if the thief changes the Sim card your phone will be totally useless. If you don't get your phone back, at least you know the thief won't be able to sell or use it either.
It is also worthwhile registering it (and other electronic items like tablets) on the Immobilise website (https://www.immobilise.com/).
I was always making notes on scraps of paper about tips and facts I'd read in books and magazines, seen on the Internet or on TV. So this is my paperless filing system for all those bits of information I want to access easily. (Please note: I live in the UK, so any financial or legal information relates only to the UK.)