It is important to find good references who knows you and your strengths and will speak highly of you.
Ask your references in advance. Make sure you are not rushing them to write you a letter of recommendation.
Provide them details about the position and why you want it and/or feel you would be a good fit for the position. See the email template below of how to ask and what information would be helpful to share.
** If you are applying to multiple positions, you can share information about your interest and fit in the field you are applying for and highlight your top company/position you are aiming for.