Most job adverts are written like a shopping list.  We'd like x and x technical skills, super people skills and someone who will work hard. Sometimes, they are just a list of responsibilites (in company jargon) and you have to guess whether you have the skills or not.

When writing an advert, you need to first think about the people you're trying to attract.  Imagine where they are, and what they want from their next step.  Then you can write an advert which is attractive to them - advert writing is more like marketing a product than shopping for one.

Once you have the picture of the ideal candidate in mind you can write to a formula:

1. Explain the context (what are you looking for, why, what kind of team)
2. Explain what the candidate will get out of the role (excitment, learning skills, working with cool clients)
3. Explain what your offer is (salary, benefits)
4. Tell them the minimum skills you need.

You don't need to write in a stilted corporate way, if your culture is cool and funky, write something cool and funky. 

Like all skills writing adverts gets better with practice - if you don't have to do it very often, ask the advice of someone who does, or look at Monster etc for some inspiration.