Depends on the person. I follow this list, even when on meds.
1. Establish a daily routine
2. Eat regularly. Avoid foods that make you feel sluggish
3. Sleep regularly. Establish good sleep hygiene
4. Exercise regularly. 30+ minutes/day
5. Make to-do lists
6. Make use of the timer. Work in intervals and take breaks between them
7. Work in an area with minimal distractions. Classical music and headphones are always with me.
8. Make use of your university's student disabilities center so they can provide accommodations, such as a separate exam room.
9. See a therapist regularly

Prior to being on meds, despite following this list, I could not get the desired work done. I have problems with memory and sleep. All I did was think and daydream (as well as experiencing the other ADHD symptoms), even whilst conversing with friends. GPA dropped during uni. The amount of stress and frustration that built up just exploded that one year, and once I consulted with my psychiatrist and therapists and was put on adderall, my mind was, and still is, more focused and quiet. I try to avoid taking meds as well, unless needed (ie: taking antihistamines daily to ward off bronchitis), but I did need adderall and it helped me so much that I was able to get back on track in life...that is, if I remember to take my meds daily. Once I am more stable and learn how to control my symptoms, I probably won't need the help of ADHD meds anymore.

Fight the ADHD stigma. If you try to follow any sort of practices like the ones I've listed, and they're not working and/or things are spiraling more out of control, maybe ADHD medication could help. There are many medication options so you'll probably have to experiment with some and consult with your psychiatrist often about any unwanted side effects, etc.