HOW TO REQUEST REFERRALS
Your supervisors, other leadership within the company, colleagues, customers, and vendors, among others, are all excellent options.
Request written letters of recommendation. Being able to list someone as a professional reference is good. However, getting a written letter of recommendation is much better, which can expedite the hiring process and helps to validate your qualifications, skills, abilities, and work performance.
Timing is everything. The best time to ask for referrals is when you are about to leave a company.
You just landed a new job and didn't need this. If your offer is contingent on a reference, it is best not to resign. However, five years from now, it will take a lot of work to go back to these people and ask for a reference letter at that time.
Thank your potential referral source, and share your enjoyment in working with them and how this will benefit your career. It is best to ask many people as some will likely not get back to you.