Pointers For Your Proposal
Once you start on your porposal, you will realise that it is almost like a mini version of your thesis, minus the results and findings. Hence, you should treat your proposal as you would your thesis, and spend the same amount of effort and time in producing it. It is not surprising for students to take up to six months to prepare their research proposal. A good research proposal is not something that you can create overnight off the top of your head. Ideally, you should create at least three drafts based on multiple discussions and feedback before your actual submission.
At least, you may only need to revise certain segments of your proposal and resubmit, but in the worst case scenario, your proposal will be rejected and you will have to redo it from scratch. So why not put some effort into preparing a good proposal from the beginning and avoid the potential hassle of having to resubmit.
Follow the requirements
Every university has its own structure for thesis proposals, so make sure that you adhere to these requirements. There is a possibility that the committee and administrative office will reject your proposal - no matter how great, promising or Nobel prize-worthy it is - if you fail to comply with their regulations, and the last thing you would want is for your proposal to be discarded because of mere technical issues.
If you are unsure about the proposal structure, apporach your graduate studies department for a thesis guideline. You should also find out the deadline for your proposal submission as the university board or committee has selected dates for proposal review.
Use proper language
In general, keep your sentence short and succinct, and avoid ornate language as well as excessive use of jargon. You should also shirk away from net-lingo and colloquial language as you are not going to impress anyone if your thesis proposal looked like something straight out of your Whatsapp chatroom. Remember, you are going to win over the commitee with the content of your thesis, not the use (or abuse) of language. The university commitee also consist of experts and veterans of the academia, and a proposal with informal language won't do much in your favour.
With that said, if you are not confident with your language proficiency, have your friends or family look over your thesis. They might not understand the more intricate elements of your proposal, but they should be able to spot the basic grammar mistakes or unusual sentence structures.