You know I am really happy to see someone is actually asking the question rather than putting together their "wish list" and expecting someone to fulfill it all. So kudos to you.
You should be looking for someone with a decent number of years experience as well as a good set of examples of what they have done. Depending on your project you will want someone that has a skill in one of the following...
1) A server-side language. Preferably the language you want the site to be developed in. They should have a lot of experience in one of the following... PHP/ASP.NET/Cold fusion/Ruby/Perl. This is going to be the code that most of the pages will use to put together dynamic pages and shopping carts etc.
2) Design experience using CSS and familiar with the differences between browsers and how they render CSS code. And if your site is going to get really "flashy" then ask for something like Flash experience. You might ask for some experience in graphic design and image manipulation if you are looking for very visual sites (like a game site for instance)
3) Client side coding like Javascript is usually a must because this is going to handle the code that your server-side language won't. Things like drag and drop, manipulating controls on the page like hiding and showing, fading etc. An extra bonus would be to ask for familiarity with AJAX and or a framework like scriptaculous/prototype. I wouldn't make it a requirement but it would be an added plus if they knew.
4) Using a database with the website. This is a must. If they are into PHP they should have experience with MySQL. If they deal with ASP.NET they should be experienced in MS SQL Server. Some developers have both which is good and always a plus. Pick which database type you will be using and then get a developer that can match it and its relevant language. If you choose SQL Server, make might want to consider making the pages with ASP.NET. If you are using mysql then you might want to consider using PHP for your server-side language.
A good designer/developer will have a combination of the three. You can find people who have PHP/CSS/Javascript with maybe AJAX and flash experience as a bonus or you might find people who are ASP.NET/CSS/Javascript with something like Atlas experience or other AJAX knowledge through Microsoft platforms. etc.
Anything up and beyond these should be related directly to what you want on your site. If you want osCommerce carts etc, then ask for osCommerce.
I just hate it when they put up web developer jobs and ask for things like knowing C++, VAX, avatar creation, how to use a kitchen sink, and fill in the blank off the wall skills when none of them apply.
Hope that helps!
This post has been edited by Martyr2: 9 Aug, 2008 - 11:20 AM