This is really a very general vague question. There is no one magic bullet for writing a winning grant. Grants are technical and require skills and the information that is being requested is important. Instead of asking how to write a winning grant maybe the better question is how is the best way to write a competitive grant for XWZ corporation and provide more information regarding what the funder is asking.
Report Vanessa's answer
First you need to know who your funder is, know their organisational history, the type of businesses they have funded in the past, and how much in average they usually support with in cash.
Also make sure your proposal is not beneficial to you alone. In as much as it is to improve you business, it has to be for the greater good of mankind, to solve human problems.
Lastly, there has to be a level of financial commitment from you! Don't make it look like your funder will bear all the financial burden for you, you need to have some capital to show how committed you are to the proposal.