ProBlogger got some pretty good stuff there, I've subscribed to it's RSS and all the posts are useful, for me I think. LiewCF recommand it too.

I've been blogging for some time, and yes I do feel that my Eng improved alot since then.

It's all depends what kind of blog you wanna make.

If it's a personal one, you wont have any restrictions how you wanna write your post, whether it's broken language, vulgars, sensitive stuffs, etc. You own it so you should be free to express what you want, and of course at the same time you've to bear with the responsibilities of what you write there.

For those who're concern bout making money from blogs, they way you write things will be limited as you've to keep an eye on the traffic, rankings, SEO stuffs etc. I'm not into this section so I guess let the pros answer this.