Having ridden street for a few hundred thousand kms, and almost 14 years, I've occasionally had to MacGiver a few impromptu things to make it to my destination. Thought it'd be neat to start a thread so everyone can share their tips and tricks. I'll start with a couple that come immediately to mind:
1) Carry a roll of black electricians tape with you. Two or three strips arcoss the top of your faceshield will act as a visor when riding into the sun. On one end, leave a bit of a tab folded over for easy removal on the fly. If you find yourself caught out, most gas stations sell this item.
2) When freazing your butt off and you still have a way to travel, place a newspaper in your jacket. You can get the leftover one at any Starbutts, or cough up 50 cents yourself at the next gas station. You'll be amazed at how effective an insulator this is.
3) Pop a couple Advil before a long ride (consult with your Dr. first) It can make a huge difference.
4) Cycling shorts with the padded crotch can add smiles to your miles, and fit well under leathers.
5) Don't use the sponge end of gas station squeegees to clean your visor. Sooner or later a little rock caught in there will scratch the hell out of it and you'll be out $50, and be looking cross eyed for the rest of your trip.
6) Stop and enjoy the scenery more than you do now. It'll only add a few min to your time, you'll enjoy your riding more, be less fatigued and can take a raft of cool pictures.
7) When facing traffic on twisty roads pass all slow traffic on passing lanes, then ride at the legal limit, or match the cars speed behind you. You'll then have a clear run at the twisties when they arrive and will catch up to the next slow group in time to use the passing lane. Repeat. If you continue to speed on the straights once past the cars, you'll only catch up to the next slow group of cars in time for the twisties.
I'll add more as I think of them. Now it's your turn to share your tips and tricks so we all can benefit!