1. Explain any shortcomings/discrepancies in your application package.
Whether that be grades, lack of research experience or etc. I personally had a rough semester and I explained some of the external circumstances that contributed to my performance and the reviewer took note of it. It’s best not to surprise the reviewer so explain what you feel could be a shortcoming.
2. Consult an advisor
If you don’t already have a research, or graustes advisor, find a faculty member that is willing to help you with your proposal. Even better if they’re familiar with the specific fellowship and get their help in every aspect of your application: proposal and personal statement. For heavy research fellowships, it was important I knew what NASA was looking for research-wise. It’s important that the entity you’re submitting to, finds your research worthwhile.
3. Consult someone who has already won the fellowship.
Take any and all advice from anyone who has already won the fellowship to which you’re applying. General rule.
4. Most important: start the application and apply.