While a number of different factors can influence whether or not your project gets funded, you can improve your chances with careful research and planning.
Grant Writing Tips Sheets A series of guides and tips sheets from the NIH
Grants and Grant Writing Articles on grant writing from Science magazine.
Proposal Writing Short Course A step-by-step online course from the Foundation Center
A Guide for Proposal Writing A downloadable guide from the National Science Foundation.
Grant Writing 102: Tips from Successful Grantwriters Specific tips and words of wisdom from successful grant writers.