I'm not too versed in the subject of becoming a better poster, but I think I can offer a few suggestions.
New posters should focus on what they know, but at the same time they should try their hand in all areas of the forum. I've focused on the bar since I learned about it and now I don't think I'd be very recognizable in other sections.
Unless you feel completely solid on a topic, don't make huge 'earth-shattering' statements like "Wrestling's Current Situation Is Your Fault". Threads like that will probably get you heat...bad heat.
Don't start repping until you get 50 posts and get a little bit of rep for yourself. People may end up labeling you as a noob before you even get off the ground.
Don't be afraid of experienced posters. If you one up them without actin arrogant they will probably react in a positive manner.
I disagree with IC25. Use vocab that you feel comfortable with. If you try to use big words that you don't have a firm grasp on you may come off as a pseudo-intellectual which has a worse effect than using more simplistic diction.
Avoid txt words.
Instead of using 'vocab' words, you should work on grammar and syntax. More people will read your posts if they look well organized and coherent.
I can't think of much else off hand, but being respectful and staying informed on your topics will help you get by.
How's life in a bigger prison?