We're going to advise the 3 P's
- Prepare (for the worst); and of course
TFL have clearly stated that the Central, DLR and Jubilee line are going to be jam packed and all other lines are going to be busier that normal - so whatever line you're using, leave plenty of time and this tool is a must: http://www.getaheadofthegames.com/travelinaffectedareas/city/london-public-transport.html#
Prepare for the worst
It breaks on a normal day when no-one's even on the train, so let's just multiply that by a few 100! There's not much we can do about things like signal failures, but carrying a bottle of water will really help! Even if you can handle oven-like conditions, that passenger looking a bit faint might appreciate it - and I'm sure everyone using the line will too!
I'll leave this one to you. Alternatives included crossing your fingers or carrying a lucky charm but be warned, if your lucky charm is a bicycle or suitcase... you will not be liked!
Good luck and God save the Tube!