* Eat 4 whole eggs per day (roughly 1 egg per 50 pounds of body weight) and 1/2 cup (dry) cooked oatmeal with a handful of frozen fruit to keep arteries healthy. Cholesterol is like a precursor for testosterone, also the sulfur in egg yolks help preserve and rebuild connective tissue.
* Take a 30-50 mg zinc tablet a couple of times per week (not every day or you'll start feeling queasy). Zinc and other metals are catalysts which speed the chemical reactions in your body, raising metabolism and strengthening your immune system. It's also been linked to higher T levels.
* 1500/1200 glucosamine chondroitin and MSM for joint health. I take Animal Flex which works about twice as well as the next best joint supplement I've found. This also allows you to lift heavier and raise T.
* Lift heavy at the gym 4-5 times per week. For example, 12" box squats with 225 pounds for 15 reps, 315 pounds for 10 reps, stuff like that. The more brutal the exercise, the more your body overcompensates and raises T levels. I benched 225x9 and 300x1 on a 4 day legs/push/pull/shoulders split in my late 20s. Now on a 5 day Mike O'Hearn split for last 3-6 months. Proven lifts: 225x10 and 275x2 bench, 365x3 box squat, 365x3 deadlift but those were all relatively easy because I've been focusing on joint strength and extrapolating 1 RM lately. Planning to test 315x1 bench, 405x1 box squat, 405x1 deadlift at the end of this 3 week on/1 week deload cycle, then will add in heavy 7 sets of 3 and start working towards 405/495/495 over the next year or so. YouTube's been invaluable for reverse-grip exercises and other variations that prevent plateaus, so I'm gaining strength faster now than I was in my 20s (I was also broke then and wasn't focusing on nutrition enough).
* Glutamine 3 times a day to heal leaky gut caused by eating legumes and nightshades for a lifetime, which resulted in acne, joint pain and inflammatory weight gain. Planning to drop to once a day now that my acne is gone.
* Breathe right strips for sleeping. My narrow palette/babyface tightened my airway and left nowhere for my jaw to grow during 20 years of elevated growth hormone from the gym. This affects a lot of people, especially anyone with let's just say geeky facial features.
Figure out any deficits you might have. In my case, sleep apnea and leaky gut had caused (what I think was) hypothyroidism and absolutely killed my mood and motivation over the last few years. The last 3 months or so have been life-changing.
I feel much better but find that I sleep 9 hours a day from all the workouts. I've been congratulated by strangers at the gym who saw my body fat transition over the last year, which really helped my self esteem. There is no secret to getting in shape other than educating yourself and being consistent (not missing workouts or meals). I've never tried over the counter testosterone boosters but might think about them after 45. I won't bother until I hit permanent plateaus.
Disclaimer: I've never had my testosterone levels tested, so this is all anecdotal. YMMV.