How do you get started writing a proposal?

Summary:

Quick tips to for quick starts.

If you've done the assessment of your organization, you've already got a
good start. Make an outline, using such headings as: Background (History
of Organization), Problem(s) or Need(s), Objectives, Methods, Timeline,
Evaluation, Budget. As you fill in the outline, make sure each problem
you mention leads to a related objective and a plausible method for
reaching that objective.

http://granthelp.clarityconnect.com has some more ideas for getting started, and other resources.