What makes a job/job description stand out?

What makes a job description stand out?

I've been tasked with making a couple of hires for software developers at my company. We are a "mature" startup and primarily .NET shop that focuses on C#, ASP.NET MVC, and jQuery/WCF. I've seen some interesting job descriptions that ask to individuals to submit code, or solve some kind of logical problem – I assume to do some pre-screening. Is this effective? Assuming a job description is a match on your skill-set, what are you looking for in a job/job description?

Happy to provide more detail if it helps.