Read the RFP or grant guidelines carefully.
If there is not a good fit DO NOT proceed. You may have a fabulous program doing important work, but if it does not match with the funder’s interest you are wasting your time. Not only will the proposal not be funded, but you may annoy the funder to the extent that it will jeopardize funding of another project.
Read the instructions. Read them again.
Then follow them, even if they seem unreasonable. For instance, if there is a page limit, DO NOT exceed it. Ignoring the requirement may have several consequences. The funder may not consider the proposal at all. Or, reviewers may only read the proposal to the page limit. At best, the reviewer will be annoyed. It is not good to annoy the reviewer.
Be clear about what you want to achieve with the grant.
The more focused the project, the clearer your proposal narrative will be. It is tempting to be overly optimistic about what you can achieve with a particular grant. DO NOT give in to this temptation.
Understand the review criteria.
Make sure the proposal reflects the priorities identified in the review criteria.
The budget should match the proposal.
This seems obvious, but as the proposal is developed the details change and it is easy to forget to modify the budget. Some reviewers read the budget and budget narrative first. If these sections are not clear, a favorable review is at risk.