There are some cool embedded videos of exercises you probably haven't tried so check those out.
In it is some advice on building a strong midsection from the perspective's of myself, a bodybuilding coach, and guys such as Mike Robertson that trains some athletes.
The real keys lie in the commonalities of our approaches: Nobody uses crunches, and we all understand the importance of train the anterior core to develop core stability, strength in torso extension, rotation, and anti-rotation functions.
Of course anything with firing neurons realizes that nutrition plays a huge part in being able to see the fruits of your labor, and so bodybuilding coach Scott Abel drops a good line:
Diet plays the biggest role here, and it's a deal-breaker. "No one can out-train an inconsistent or improper diet," Abel says. "And if your own metabolic set point is such that having quilted abs is not your genetically natural predisposition, then you'd better have expert help in achieving that look."
As for aerobic training,
Abel says to practice caution here. Hours a day of steady-state aerobics can lead to a suppressed metabolism, burned-out adrenals, and even an unexpected weight gain. "As I always say, force the body and it reacts. Coax the body and it responds."
To sum it up be on point with your nutrition, then skip the aerobics classes and crunches, and instead train your core in ways top trainers in various sub-fields of fitness know work.