The first how to get lean muscle rule is this: lift progressively heavier weights. That's it. If the weights you lift gradually get heavier and heavier, you will build lean muscle. Of course you have to make sure that each workout you lift, the workout is more intense. For example, if you're lifting 20 lbs x 10 repetitions your overall load is 300 lbs. If you think you can take 30 lbs but you only do 4 repetitions your overall load will be 280 lbs. This means that either your muscle hasn't had enough time to recover, your diet isn't providing enough sustenance for your muscle to grow, or a combination of the previous two.
No matter what you might have heard about, "sculpting and defining" your muscles by lifting light weights. It's a myth and lifting light weights will only burn calories (not even fat!). That's all. So forget about it. "No pain, no gain" was created with how to get lean muscle in mind.
The second how to get lean muscle rule is this: lift high reps, not high sets. This basically follows the tenet of building lean muscle, "low volume, high intensity". It's pretty common sense really. If you lift a heavy weight 2 or 3 times, your muscle won't be given enough time to react to the force. However, if you lift it 8 to 10 times, your muscle will definitely notice it and work harder to grow to better oppose the force it's subjected upon. Why not high sets? Because between each set, you're giving your muscles a break. That means your muscles are not being pushed to their utmost limit, meaning there is less muscle to repair, meaning less muscle grows.
There are obviously more rules to building lean muscle, but if you keep these two in mind, lifting progressively heavier weights and doing more reps and less sets, you will definitely see muscular growth, no matter what your body shape.
