You might want to approach your professors for letters of recommendation. Professors get lots of these requests, and they are very time-consuming—they’re not a casual task. For most applications, letters of recommendation are critically important to your success (they’re not just generic quick character references, but detailed assessments tailored for each student and each position). So follow these guidelines carefully, and be prepared and proactive:

• Ask for the letters well in advance of the deadlines.
• Ask the recommender if they would like to meet with you first to talk about your plans.
• 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. (They are ordinarily assumed to be confidential.)
• Provide copies of all the forms required, including stamps on the envelopes the recommender is to send separately.
• If forms are online, provide complete links and access information (passwords, codes, etc.) that may be needed.
• When completing application forms (electronic and paper), 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.).
• Give the recommender a copy of the written statement or letter you will be sending with your application (including any Statements of Purpose); if you plan far enough in advance, the recommender might be willing to look at a draft of this letter and make suggestions for its improvement.
• Give the recommender a separate note indicating what elements of your qualifications the recommender should emphasize, a list of the courses (with quarters and grades) you have taken from the recommender, and possibly a writing or creative sample from one of those courses to remind the recommender of your work. Ask your recommender if they would like a copy of your transcript. 
• 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!