A theme is the layout / design of a blog.
It is important to select a theme that fits the ideas of your blog at the beginning of your project. Simply because you should be planning in front and know what layout you require.
Another minor reason is that screenshots maybe taken of the blog and displayed on other sites, changing the theme just makes the site a little dis-orientated when users click on the image and are then faced with a different looking site.
Point to consider may include:
1) Navigation – do you require drop down navigation links.
2) Widget Ready – Premium themes are built so you can just insert a widget you require.
3) Ad Space – will you be inserting banners or ads, if so you need the space to fit them in.
4) Ready optimised
There are many places where you can find themes, I’m currently compiling a list of my favourites which I’ll add shortly, so bookmark this page and check back soon.
In the mean time, if you have any great themes you wish to show off, please add them in the comments.