So your organization needs someone to write a grant? Don't know where to start in finding and applying for grants? Start Here:

[edit] Steps

Decide if you are hiring a consultant for a single project or someone for a longer period of time. This article applies to the former.
Define the project. Know exactly what you need, and have a good idea about the kind of person who can provide this for you.
Decide if you want to hire them on contract or if you would like to employ them permanently.
Start looking for people who fit the job description. Look online, but also talk to people you know. Ask, "Do you know anyone who has experience writing ____ grants?"
Collect resumes and references.
After reviewing applicant data, set up interviews with the top candidates.
In an interview, describe in detail the kind of work that your organization does and the kinds of grants for which you plan to apply.
Once a grant writer has been hired, provide him or her with enough information to write a thorough application. It may take over two weeks for the grant writer to learn your organization, its functions and its needs.
Provide feedback to the writer throughout the process.
Remember to adapt each application to the specific funding organization. Don't just cut and paste!
Write the grant applications and perform a review with the writer. Decide if you wish to continue working together.

[edit] Tips

This was written for people looking for grant writers hired on a short-term, contract basis. However, it also applies to those looking to hire writers in general, or just to hire contractors or consultants.
Allow extra time for revising and submitting grants.
Remember that grants are competitive and not guaranteed.
Many grants only provide one-time funding. After the end of the grant period, you will need to start applying for new grants.
Keep in mind that grants are legal contracts!