Be sure to give credit where credit it due. If you quote a story from another auther, say so, give them a link back. Be aware that you can be held liable for copyright infringement, plagarism, defamation of character, and all that other stuff that journalists have to contend with, so play it smart and give credit when using someone else’s words or pictures, and look for copyright notices and creative commons licenses to see what is being said about reusing content.
When setting up your blog consider the readability of the layout, and try to maintain a similar post style throughout, as there are many blogging templates, it is often confusing to readers as to what is commentary and what is quoted stories, etc. So deciding early in the game as to how your are going to layout your posts can save you hassles in the long run.
Find other people who are posting about similar topics, do a search through technorati.com and comment on thier blogs, do a trackback to your blog, or mention them in your blog so people, thoughts, ideas can be linked together and people will be able to find similar interests and your blog easier.