Faculty get lots of requests for letters of recommendation, and they are very time-consuming for them, so follow these guidelines, be prepared, and be proactive:

• Very good general advice is here, best looked at well ahead of time: https://www.ucdavis.edu/majors/blog/how-to-request-letters-of-recommendation-for-grad-school
• Ask for the letters well in advance of the deadlines.
• Be discerning about how many letters you’re requesting, so faculty can allocate time equitably across the many students making similar requests at the same time. (Especially with grad school applications, very careful preparation and suitability is much more sensible than “flooding the zone.” Consider explaining your application choices to your recommender.) 
• Ask the recommender if they would like to meet with you first to talk about your plans, and whether they are able to write you a strong letter of recommendation; be prepared for them to decline. 
• Important: inform your recommender in advance if you do not intend to waive your right to review the letter of recommendation, and ask if they are still willing to provide one. (Letters are ordinarily assumed to be confidential—the default is for the applicant to waive their right to review.)
• Provide complete links and access information (passwords, codes, etc.) that may be needed. Make sure that you have filled in as much information as possible, as accurately as possible (e.g. the recommender’s work address at UCD, their faculty position, department, etc.).
• Remind your recommender of courses you’ve taken with them (with quarters, grades, writing or creative samples) and other ways you’ve interacted (e.g. in office hours, clubs etc.), mentioning instances of how you demonstrated creativity, leadership, recognition, growth etc. under their guidance. Ask your recommender if they would like a copy of your transcript. 
• Give the recommender copies of your CV, and your portfolio if applicable, plus any statements you will be sending with your application. (If you plan far enough in advance, the recommender might be willing to look at your drafts and make suggestions for improvement.)
• Provide a schedule of deadlines for applications.
• Thank your recommender!

Check back with the recommender a little before the deadline to inquire, gently, if the letter has been sent or uploaded. If you can check the status of your recommendations online, you may want to send a reminder along with any links (they can easily end up in Spam folders). If you change your plans (e.g., by adding applications, or not applying), inform your recommender straightaway. In short—it’s a good idea to look after your recommenders when they’re writing letters about you!