To improve your proposal writing skills and increase your chances of getting hired on Upwork, it's important to start off by showing that you've read and understood the job posting. Within the first sentence of your proposal, you should mention something specific from the job description to show that you're paying attention to the details. This will help you stand out from other applicants who may not have taken the time to thoroughly read the job posting.
Another important aspect of a successful proposal is to show why you're a good fit for the job. You can do this by highlighting your relevant experience and skills, and explaining how they align with the client's needs. Keep your writing concise and to the point, and use bullet points if necessary to make it easy for the client to read and understand. Additionally, including a relevant example of your work can be a great way to showcase your abilities and prove to the client that you have the skills and experience necessary to complete the job successfully.