A great resume is key as well as a portfolio site. I always bring my laptop to an interview incase they want to see code; I always make sure I have examples on my portfolio site that are up to date and have to do with the job I'm applying for, etc...
What was funny - my 2nd last job - they need a Wordpress developer and although I'm damn good with PHP, I hated Wordpress - so the weekend of the interview (interview was on monday) I spent about a day reading the WP docs and built a website on my portfolio site with a custom theme, custom plugin, made it responsive, etc... (stuff they would expect) - showed it to them during the interview and got the job (I like to think it helped) - it didn't come out until months later that I learned WP in a weekend (roughly) and everyone was pretty impressed.
My current job - they were looking for a very specific skill set (Rackspace Cloud administration) and actually were more impressed with one of my side projects then any job I held. So you never know what someone is looking for - could be professional experience, could be a side project.