this is purely from my experience, post a comment if you have a tip:
1. deflate the tires a little. this will increase the contact patch between the road and your tires and help prevent sliding/gliding on slippery roads.
2. ride slow. i know its frustrating and irritating to some to ride in the rain but try to enjoy it. be a masochist once in a while. this will also help prevent your tires from planing — sliding/gliding on water and get you home in one piece.
3. on the road, be mindful of the things and specially the vehicles around you. if you're riding slow they will pass you.
4. be patient. spashes from other vehicles will eventually find you. its part of riding in the rain.
5. if the rain or wind gets too strong, seek shelter. let it pass and when things get manageable, ride on.
6. before taking that ride in the rain, think wether you can wait for the rain to stop.
7. when you finally get home, take a quick bath. you stink.
8. dry your steed. be it steel, aluminum, titatnium or carbon, some part of a component or another is bound to rust. besides, it got you home right?