There are many excellent books and on-line resources that give step-by-step "how to write a grant" information.  A couple of good ones are:

The Foundation Center's Proposal Writing Short Course:
Takes you clearly and succinctly through the basic elements of a sound proposal (executive summary, statement of need, project description, budget, organizational information, and conclusion).  Tailored more for proposals that will go to foundations.
 
Writing Effective Proposals (California Department of Education)
Overview of the components of an effective proposal, with an emphasis on the areas generally required in California Department of Education grants.  Relatively short and to the point.  
   
US Dept. of Education Grant Application Technical Assistance Resources
Answers questions and gives tips on applying for a federal grant.

Donna Fernandez' SchoolGrants site
:
This site gets my vote for the best and most comprehensive resource for grantwriters that there is. She includes links to open competitions, tips for writing grants, sample proposals, and much more.  

Grant Proposal.com
Thanks to Stephanie Starmer for finding this one. Lots of good resources here, including Six Guidelines for Grantwriters and Active Verbs for Grantwriters.

Teacher's Network.org
Many more links to grantwriting "how-tos", including The Elements of a Grant Proposal, Why Proposals Get Rejected, and the Corporation for Public Broadcasting's Grant Proposal Writing Tips

Grants 101: CUSD Presentation

Here is a copy of the powerpoint presentation on Grant Development and Proposal Writing, as well as the handouts with additional hints and information for grant planning and writing.