Instead of being afraid of saying something wrong that causes you to lose the whole proposal, you should be more concerned with saying a bunch of little things that dilute your message. This happens far more often. Maybe it's because people take a while to get warmed up before they start writing anything decent. Many of the examples below are things that people often write out of habit to help them get started. You can write a better proposal just by breaking these habits.
It's not about you. Your proposal should be about your customer. Instead of saying:
* When you were founded
* Who the founder was
* How much you have grown
* How long you have been in business
* How big you are
* How many employees you have
* How many cleared staff you have
* How many locations you have
* What your mission is
* About your other customers
* Where you are located
* We're ISO certified
* We're certified in…
Say how your size, age, location, or other qualification will benefit the customer. Make it about them and not about you.
* Don't tell the customer what their needs are. If you feel the need to document the requirement, do it in the form of a statement about what you are going to do to fulfill the requirement.
* Don't summarize requirement. You can show your understanding by stating what you will do to fulfill the client's needs. When you summarize the requirement, it's redundant with the RFP and runs the risk of being patronizing or just plain wrong. When you say what you are going to do and how the customer will benefit, they will recognize it as something they need (or at least something close).
* Don't use passive voice. It's a grammar thing. If you don't know what it is, look it up. It's important.