7. Add weights slowly.
The main reason people plateau and stop gaining strength is that they go too heavy for too long. Abandon your ego and do your main lifts using 10% less than the most weight you can lift for the given rep range. Increase the weight each session — but by no more than 10 pounds — and stick with the same lifts. You'll rarely plateau again.
8. Take to the hills.
Cardio is a must if you want to be lean and healthy, but long-distance running or cycling increases levels of hormones that break down muscle tissue. To get stronger while getting leaner, do cardio in short, intense bursts. Go to a moderately steep hill and sprint to the top, then walk back down. When you're ready, sprint again. In your first workout, do only half as many sprints as you think you could. In your next workout, do two more sprints than you did the first time. Continue adding two sprints to your workouts until you can't improve anymore. Then do sets of sprints.