I guess I worry about recommendation letter is that I am more of a "quiet" person; I didn't ask a lot of questions in class so not much attention was drawn. I wonder how they would write the rec if they agreed to do it; I mean if it is not a good rec, I guess it is no point to ask (I was told, a not-so-good rec is like an automatic rejection
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Here's what you do - think about a professor whose lectures you enjoyed and found interesting, or look at the bios of the school faculty on the school's website and find someone who has had a career path that seems most interesting to you. Then, email that professor something along the lines of, "Hello Dr. so-and-so, I don't know if you remember me, but I am a P4 student, and I really enjoyed your lectures on blah-blah. As I reflect back on my time in pharmacy school and on my future plans, I realize I am interested in pursuing a residency, but still have questions I am trying to figure out. I would really appreciate meeting with you and gaining your insight on residency training. Could you please tell me what your office hours are or when would be a good time for us to meet in the next few weeks? Respectfully, ice712 ak.a. the person who pays a good chunk of your salary" (don't actually include that last part)
After meeting with this professor and having a conversation with them, share with them your concern about getting a letter of recommendation, and see what they say. Maybe they have a mini-project you can help them with that will give them a better idea of what kind of person you are, and then they will feel comfortable writing you a good letter of recommendation. If someone agrees to write you a letter of recommendation and you are not confident it will be a good letter,
ask them what kind of letter they plan to write - you don't have to wonder, you can ask, that's totally a reasonable question.
Even if you don't end up doing a residency, building skills in networking and developing relationships will take you far in your career. No one gets anywhere in life without the support of other people in one way or another. Now is the time to practice those skills (i.e. to mess up, be awkward, and learn from your mistakes), while you're still in school. You don't have to be a super extrovert all the time, but challenging yourself to go out of your comfort zone every now and then is usually well worth the risk.