1) Wait for at least one person to post before you do... it makes the topic look less monopolised and you look less desperate to post. *whistles*
2) I generally like to wait for the other half of my interaction to post before I do (if they don't I poke them until they do), unless I have preconceived subplots for the character I'm playing in the RPG, or I feel particularly motivated to move on (usually after a week or two of zero interaction). I know about the whole 'keep the RP moving' and stuff.. but sometimes it's so hard to squeeze the words out of your brain...
3) Solid post? Eh, at least three paragraphs with four forum lines in them - that's a decent post. Solid posts could be about the same length but plus character introspection/interaction. I try to make my posts at least one screen long on Wordpad. I don't discriminate against what people do or do not include in their posts, (unless it's the horrendously obvious) nor do I have a particular preference for long or short posts. (As long as somebody posts... I'm happy)
4) Um.. hehe.. not yet? I'm sure I will be, eventually, if I keep those 2000-word posts up >< What I like for description in posts: Usually the character's mindset or thinking style, or other characters seen through the character's eyes. (Especially if it's mine.. I get all eager to post when it's my characters people are describing *easily excited*)
5) RPing for me is sort of like writing fiction but with a handy plot and premise provided for you so you can enjoy the ride and won't ever have to worry about where your 'fiction' is going. Reading people's signups to RPGs you have joined is like fiction lottery - you don't know what people are going to sign up as, nor how their characters are going to interact, nor any of the subplots that might develop, but you keep going back for more because it's addictive. I realise that I haven't answered the question properly.
6) Lost interest in one roleplay but I think I was one of the last ones to post there anyhow ^^; And I feel really guilty if I sign up for an RPG and I back out in the middle, lately I've been trying to cut back on that (*cough* last year it was a different story *hides*) so I make my own characters as interesting to myself as possible (ie. add subplot, draw the characters, humorous narration, etc) so that I won't lose interest in writing posts. However, if you lose interest and also are unable to fake interesting posts, maybe it's better to stop posting entirely?? I mean, you should talk to other people and/or beg them to help integrate your character back into the RP first, though.
7) I'm rather for being lenient, cos I'm not such a prize myself. Oftimes if the rules part of the RPG dictates how often you should post then naturally the RPer should try to adhere to the rule, or at least ask/beg the GM for more time if you really can't cut it.
8 ) I usually skim through it first, and then when I'm posting I open another window and reread it in detail. Very often I save the page for reference when I'm writing more complicated posts.
9) If the participating RPers' characters are interesting, then automatically the RPG will become interesting to me, whatever the theme.
10) Not much bothers me unless it's bad grammar or people being unreasonable about little things. Neither of which happens much in this forum.
11) I dunno. Always? I'm always procrastinating my posts till the last minute but when I actually write them the enthusiasm comes up to the surface again. Lately in Otherworld I found that I like to write Erensuge and Ortze's aunts more than Ortze himself... this is bad o_O