1. Eat a healthy diet
    1. Exercise (strength training and cardio)
    2. Lose weight (if you are overweight)
    3. Get enough sleep
    4. Decrease/Manage stress 6.zinc/vitamin D

Here's a good handout from the University of Wisconsin which covers the above but also discusses a few supplements you might want to consider. http://www.fammed.wisc.edu/files/webfm-uploads/documents/outreach/im/handout_testosterone.pdf

Is this all we can do to increase testosterone naturally?