Be careful where you place cables and wires they can trip you up! Cables which are tied up should be untied and it's best not to run them under carpets where they can be trampled. Always check the wires for damage before use.
Don't use lights for inside use outside they're not made for those conditions. If lights are damaged don't use them and never remove or put a bulb in without turning the power off.
Beware old lights may not comply with up to date safety standards. If you're buying new lights look for the BS kitemark. If you buy 2nd hand lights always get them checked out by a qualified expert.
When dealing with electrics it's always better to be safe than sorry. Have a great Christmas and a happy healthy and prosperous New Year.