So, I was chipping away a while back at my version of the Exercise Bible not too long ago and while I was doing the tablemakers and the hindu push-ups, something kind of struck me. I realized that I could make these two exercises more difficult with a modest tweak in how I perform them, each one adding up to more core work in the exercise.
The hindu push-ups sometimes get lost in the shuffle of trying to find exercises that develop strength because part of the exercise has very little in the way of muscle contraction as you return back to the starting position. Often times, I eschew them in favor of the dive bomber push-up, which requires you to back-track during the dipping movement. There's no doubt that makes it harder than the hindu push-up. A good way to make it harder as you return to the starting position is to pull yourself back to the starting position with your abs, rather than pushing yourself back with your arms and shoulders. It may not make it as hard as the dive-bomber, it does help you squeeze more out of the former.
You can add more ab work to the tablemaker by never resting your butt on the floor. Instead, rest your bodyweight on your heels and your hands. Raise and lower yourself upwards and downwards, NEVER PUT YOUR ASS ON THE GROUND! A friendly reminder when you're doing the tablemaker: make sure your head and neck travel with your torso. Don't raise your torso while keeping your head stationary.
While I don't do these exercises when I'm doing the Bible, I thought that while I'm going over the finer points of certain BW exercies, I'll mention a pointer on one of my favorite ab exercises: The spider-T push-up. When you're doing this push-up, make sure that as you descend downwards, make sure that you keep your shoulders straight. Don't allow the shoulder on the side of your moving knee to sag. This assures that you're not losing any of the difficulty of the exercise. It also may spare you some shoulder soreness afterwards.
I could keep going with small details like this but I think I'd be better served to tell you to keep yourself focused on what you're doing when you're exercising. Getting the most out of a given exercise by paying attention isn't just about the move as you've learned it. It's also about realizing that you might be missing out on a small tweak that can get you more results. As you tire, your body will instinctively try to make the exercise easier. It's up to your sharp mind and your willpower to realize this and force yourself to maintain the intensity and form. That's why paying attention and staying focused is so important when you're training.