The Office of Sponsored Research is happy to give your proposal a critical review before it's submitted, but as many people as possible should read your proposal and give you critical feedback before it goes out. Please be kind when asking colleagues and friends to read it, though. Finish a draft, then circulate it to your readers giving them enough lead time to give it a good read. Collect their comments, then revise. Don't give a new draft to someone who's still reading an older version.
You have one chance to make your first impression with the reviewers; the abstract/summary and the introductory section should be perfect and should grab the reviewers' attention. If your friends/colleagues can only review limited portions of your proposal for you before submission, these should be the sections they read.
The reviewers are not necessarily experts in your field and may be reading your proposal on the check-out line in the grocery store. Take this into account when you're writing.
If you need substantial help with your proposal, please begin communication with our the Office of Sponsored Research well in advance of the submission deadline.