Research and study the requirements of the funding agency. The 44 different federal funding agencies have varying requirements. It is essential that you know exactly what the agency you are applying to requires.
Read the request for proposals carefully. Underline any keywords or "hot" issues outlined in the request for proposal. Addressing exactly what the request for proposals outlines will make your grant proposal more compelling to the funding agency.
Begin the grant with a logical problem statement that outlines the benefit to society and to the funding agency itself. One way to make your overall grant proposal compelling is clearly outlining the problem you are seeking to solve. If the problem is something that is important to the funding agency, you will have a better chance of winning the grant.
Be very specific when describing the method and approach to solving the problem. Use a methodology that is accepted by your field of study. For example, if your field relies mostly on experimental studies, you shouldn't propose a case study unless you have a strong reason to.
Present a detailed project time line that is reasonable. Don't propose something that a funding agency might deem too ambitious. Conversely, don't propose a project time line that is not ambitious enough.
Outline the budget necessary to fulfill the project. The more detailed the budget, the more compelling the proposal. Details show the funding agency that you've given the appropriate amount of planning for the project.
Discuss the significance of the project on varying levels. For example, discuss short-term and long-term impacts that the project will have on the society as a whole. If possible, relate the significance back to the issues addressed in the request for proposals.