most of this stuff is great advice. some absolutely essential tips are:
. never brag infront of people. even thought you think you are a great writer there is always atleast a thousand people better than you.
.do not....DO NOT, hit steel straight away. if your stuff looks shit on a wall, it will look pitiful on a train.
.dont dress like a writer. this has been covered, but take it from me this will save you.
.never ever become cocky. once you become confident you can easily escape a situation...you will get caught. think everything through slowly and rationally. this being said, you are a writer, not james bond or tom cruise in mission impossible.
.if you are writing because it is "the cool thing to do" , give up now. no one owns writing, writing owns us. writing is a way of life and it will make you its bitch. treat writing well and it will reward you....be an idiot and prepare to get slapped.
.....pffffffffft, lighten the fuck up and enjoy writing.