a. If they're talking to someone make sure you end the conversation before you go off and do something else. It helps keep confusion down to a minimum.
b. Make sure you know which characters are yours. Don't start using another person's by mistake. It'll be annoying, confusing, and make you look really stupid.
c. Know your characters! Know who they are, what they look like, how they act/talk, who they like and/or hate. Don't write something in your Character Bio and then disregard it. It's okay to look back at it, that's why they have their own little area.
d. If they die, make sure you remember that. If the RP allows you to find away to bring them back, feel free. Just remember to tell about it happening and remember you do it.

a. If your character is not used (you posting them doing something) they will either be given to someone else until you decide to return or killed off. It all depends on their: importance to the story, level of useage prior to this consideration, the RP creator, and you.
b. If you know you're going to be gone for a while tell someone and give them control over them. Preferably someone who either knows you/your character or someone you can keep in touch with via phone or whatever.
c. No complaints.