Many of my colleagues have given great advice regarding how to secure strong letters of recommendation. Thus, I am going to share how I got my letters of recommendation. I decided to go to grad school during my sophomore year and it did not take long to realize that no faculty member at my institution knew me well enough to write a strong letter. Therefore, I talked to one of my professors and he recommended me to go to a summer research program. This provided me with my first letter (it is always good to have a strong letter from someone outside your school), as well as, enabled me to get hands-on research experience. Once, I got back I felt confident enough to ask one of my professors to hire me as a research assistant, hence, securing letter the second letter. Finally, realizing that I would need one more letter, in my senior year, I took an independent study with another faculty member so that I could work on a research project and he could get to know me better.
In summary, once you have decided to apply to grad school, if you do not have enough strong recommenders either: 1) go to a summer research program, or 2) enroll on independent study credits, or both.