You actually have something to say? Now that is cool, it will differentiate you from a whole lot of other bloggers around and is the right starting point for you.
So say it! What? You do not know how to? No worries.
Below is a basic check list to get you up and running with your idea:

1. Use WordPress! This blogging tool is not short of amazing.
   Today, version 2.
   6 has been released, with yet more great features - such as real captions for images within text - and some bug fixes as well.
   Already the previous version had been very stable.
   A robust platform for a blog that even can be used as a Content Management System (CMS) for your new site.
   So this blogging tool really rocks - or the beginner and the advanced blogger alike.
   It is free and easy to install on your server, just follow the instructions on the WordPress site, they really work great.
   Download it from the WordPress home page!
2. Start out simple! When just starting out, it is absolutely key to concentrate on what your blog really is about.
   Maximum 3 different topics.
   Period.
   Too many sidelines will distract you and your readers from the main topic.
   Focus on this idea of yours, the topic you had this urge to voice your opinion about.
   This has to be central, at least when beginning.
   You will need time for your writings on that topic alone.
   So keep your blog topic wise simple.
   
3. Avoid this plugin clutter! It is so easy becoming trapped in a chaos of "useful" plugins, that aren't really needed.
   Worse, each one of them can potentially introduce a serious bug into your otherwise functioning system.
   Some are redundant or even obsolete, depending on the WordPress version you have installed.
   Many create entries in yous SQL database and are difficult to totally de-install.
   This is not to say that there aren't absolutely useful plugins out there, but remember: you are just starting out and should do so with a clean installation.
   With more experience you will find out what plugins really are needed for YOUR site.
   To begin with, just use the very basic setup.
   That will save you lots of time you can use for meaningful articles instead.
   
4. Writing is key! Not design.
   Granted, the default scheme that comes with your installation might not be the very most visually appealing.
   With time, you will find better ones or even make your own.
   But the most important thing will always be writing of articles which catch your readers' attention.
   Save yourself time and use a simple and visually un-cluttered design without all those bells and whistles in the beginning.
   It is your message that counts.
   
5. Be smart, get advice! Before becoming a guru yourself, rely on the advice of others who already made a lot of the experiences needed, some of which just time consuming, some unpleasant.
   You do not have to spend your time making all those experiences yourself.
   Be smart! There is an overwhelming amount of advice out there, but try to be time conscious.
   Remember, you will have to write, not search the internet.
   There exist really good books and tutorials which can guide you, so you can concentrate on your main topic which will consume much of your energy during the time to come.
   

Good luck with your endeavor!