One of the most common requests I get from members at my gym is a suggestion for stronger, flatter abs. Maybe it's because we're approaching bikini season, or maybe it's the fact that crop tops are back in, but lately, a taut middle is an even hotter topic. But as usual, the best moves for your tummy are equal parts body shaping and body saving. To that end, here's how to revamp your current core routine: 

Mistake #1: You don't hit your core from all angles. Too often, people think "abs" and just focus on the rectus abdominis (RA), or the six-pack muscle. I can see the logic, given that this superficial muscle is the one that "pops" most to show the fruits of your labor. However, having a strong RA alone won't provide your body with the deep core support it needs to keep your lower back safe and strong. Another similar snafu is trying to focus attention on a particular trouble spot, like the "lower" abs. The crazy truth: There's no such thing as lower abs, at least in terms of the musculature—the rectus abdominis is one continuous muscle from top to bottom. That doesn't mean you shouldn't do exercises typically prescribed for the RA or for the "lower" abs—it just means that you need to mix up your routine to work all the muscles of the core: superficial and deep ab muscles, as well as your obliques (side abs) and back muscles. Some great moves to include: planks (front and side), hip bridges, and wood choppers (straight and diagonal).

MORE: 7 Ways to Make Planks Harder

Mistake #2: You do too many crunches. Anyone who's gotten me started talking about ab exercises knows that crunches aren't my favorite. My personal philosophy is that, while these muscles are designed to flex and bend, you're better off training them to resist those actions (like you do with planks) to make them stronger and help you stand and sit a little taller. Crunches do just that—crunch your ab muscles—and may contribute to less-than-ideal posture habits and even lower back pain. If you are going to go there, don't only do crunches (erase those 100-crunch-a-day challenges from your repertoire!) and definitely don't yank on your head and risk neck injury. To perform a correct crunch, keep a neutral spine with a natural lower-back curve, not a flattened back that's pressed into the mat—it should feel like your tailbone is pointing straight ahead, not tilted down into the mat or up to the ceiling—and pull in through your belly button to initiate the movement. 

MORE: 10 Abs Exercises Better Than Crunches   

Mistake #3: You do too many sit-ups. They were the dreaded staples of middle-school gym class, and for some, sit-ups are best left as a distant memory. They can put undue stress on your lower back and even strain your hip flexors—if you've felt that sharp pinch just above your pelvis when you come up, you know what I'm talking about. The pinchy effect may be more pronounced in the decline version, in which feet are hooked into an apparatus and the body is slanted downward. If you feel discomfort beyond the usual abdominal burn, try modifying your form. Unhook your feet (and come off the machine), and focus your attention on contracting through your abs to raise your upper body. And, by all means, don't pull on your head; cross your arms in front of your chest, just like your P.E. teacher told you to.

MORE: Core Exercises That Trim and Tone Your Waistline

Mistake #4: You rely entirely on ab exercises. You've no doubt heard that you can't target fat loss to magically get a slim tummy—or, well, any one specific body part. And it's true; if you want a midsection that Cameron Diaz would covet, you've gotta work your whole body and work it hard (just like Cam works hers). High-intensity intervals are the most time-efficient way to torch fat from all over your body, but adding dance classes, a sport like tennis or soccer, or strenuous bike rides and runs into your routine will ensure total-body fitness. 

MORE: The 7-Move 7-Minute Circuit That Blasts Fat Fast

Mistake #5: You rely entirely on exercise, period. In order to truly uncover your ab-potential, what you eat—and more importantly, how much—is just as, if not more, important than how you exercise. If your diet is more muffin tops than cut fruit...well, you know the story. Where your body tends to store fat is mostly genetic (thanks, Mom and Dad!), but stress in particular contributes to belly fat, so finding ways to manage your tension—yoga, meditation, a calming hobby like knitting, etc.—may be your ticket to the taut tummy club. 

MORE: 7 Flat-Belly Food Tricks