In order to make the job of blogging at wordpress.com easier for us all we’ll just put a brief overview of things to be taken into account.
On youtube you have these two videos that are highly informative. The first one is shorter:
And you have the second one who is longer. I’ll assume that it also is more informative, but since I’ve only watched 5 minutes of it I can’t really tell.
As another option you can see the Getting Started page by the wordpress.com people and check out what they have to say.
Another thing that you might like to do is to display some nifty code that you had to do for some reason. wordpress.com allows you to do just that and for some programming languages syntax high lighting is also provided. In case the language your code is written isn’t available just choose text as the programming language and you get it done too (but with no syntax highlighting). To see how to do that just go Posting Source Code.