1. Go to Wordpress.com and click "Sign up now."
Some people use Blogger, others use Tumblr, but I've found Wordpress has the cleanest look and most flexibility for customization.
Select a theme to customize your site:
2. Pick a domain.
You can choose any name for your blog, but I highly recommend setting your full name as the domain address (the benefits to this are obvious). To do this, enter your name as the username in the signup process. So if your name is Phil Sampson, have your user name be 'philsampson.' This will set your blog's address to philsampson.wordpress.com, which you can easily convert into philsampson.com with the purchase of a domain name.
Obviously, if your name is very common, you probably won't be able to own that domain and will have to choose something else.
To get your custom domain, click on "Store" along the left hand side navigation menu, and select "Domains":
Then enter your domain of choice to see if it's available:
Wordpress will take you through the rest of the process.
3. Start blogging.
You can post about anything you want.
The main point is to create a website that puts you in a very employable and positive light (unlike your Facebook account, which has pictures of you taking beer bongs to the face).
If you want to use your blog as a way to get employers interested in you, I suggest you write about things that they'll find valuable and relevant. So you can write about your past experiences in a particular field, things you're learning about, current projects you're working on, etc. Just be honest and donʼt over-inflate your accomplishments.
An important thing to keep in mind, though, is the quality and frequency of your posts.
A half-assed blog is more of a liability than anything. And I donʼt think itʼs super important to post really often - you just need to make it into a hobby youʼll enjoy. If that means writing one long post every two weeks, so be it. Just make it a regular part of your routine while youʼre searching for work.