I. Write because you want to, need to, not because you have to, unless of course you're being paid for it.
2. Never discount nightmares as a vivid, if frightening source of new material. Write them down, once you've stopped screaming and extricated your fingernails from your bed mate's arm.
3. Family in-jokes are generally only funny to the folks in the family. If you must repeat them as part of your story, don't tell your family. Great aunt Petunia won't be too impressed to learn, that the whole world now knows she tried to start the barbeque with a litre of paint thinner, and blew it up.
4. Stupid and inept writing is not going to be any less stupid or inept by reading it out loud. On the other hand, if reading great work out loud doesn't improve it, it could be you just can't stand the sound of your own voice.
5. If your epic novel-to-be has more than five characters, write up a glossary or character list so that at least you can keep them straight, even if your readers can't.
6. Swearing at the keyboard doesn't improve your typing or spelling, but it might make you feel better.
7. Typos and bad grammar has it place - In a first draft that no one else ever sees. Typos and bad grammar is sloppy in published work, even if it's in an amateur forum.
8. If something hurts you so bad that you could never, ever talk about it, write it all down, in all its painful detail - then burn it. Let all the hurt feelings, sorrow, and anger associated with the incident, go up in smoke and dissipate into the air, then forget about it.
9. Don't write publicly about friends without their permission. If you do, there's a good chance they won't be your friends much longer.
10. Don't even try to write anything intelligent, or even half ways readable while in the throes of PMS - just because.