1. Always carry a spoon. The number of times I could have done with a spoon is ridiculous. In a pinch you can improvise one using the lid of a yoghurt pot, but this is presuming you have an open yoghurt to hand.
2. Take every possible opportunity to go to the toilet or have sex, provided that neither of these activities offends or upsets anyone.
3. Carry a rainproof hat. Small children will laugh in your face but your mascara will not run.
4. Carry nailclippers. I can strip electrical wire with mine and open tubs of hummus with the pointy bit.
5. Rehearse ninja moves in your head in case you get mugged. This may prove fruitless but it gives you such a bad-arse attitude that casual criminals will pale as you pass. Oh and keep your bag zipped and in your lap.