The project evaluator has no enough time to read the entire proposal so but only the executive summary. Your executive summary should be concise and specific. The key concern of the Funding Organization should be briefly identified and addressed in your Executive Summary in relation to your proposed project.
The best time to prepare your Executive Summary is after you have completed your entire proposal and you completely understand all aspects and the interplay of the components of your project proposal very well.
Make your Executive Summary be your last piece of writing when you write your proposal and then insert it at the beginning of your proposal.
Always remember to give your best writing performance in your Executive Summary. Your Executive Summary will most likely form a very strong impression in the mind of your evaluator.