Try alternating strength and endurance every other workout. Strength: consider decline situps using DBs held to your chest or plates packed in a backpack worn backwards over your chest. Since I work out at home right now, my DBs only go to 40, so I hold 2 40s and fill my backpach with another 40 pounds. It helps build core strength (along with deadlifts, squats…). Endurance: consider bicycles - lying on the floor and alternating touching elbow to opposite knee with a modest tempo. Variety and intensity.
Spears’ abs are not ripped… far from it… she has a nice midsection… but if that is her idea of ripped… well… SHE NO GET THE HOT-ROX!
for nice abs… DIET DIET DIET IS KEY!!!
Don’t be afraid to use some real weight when training abs.
Hang upside down and have some one hit you across the stomach when you come down from a situp. It worked for Rocky.
Before doing your next abdominal exercise, think, what exactly is the function of the abdominals?
They contract, and decrease the distance between the upper and lower body. In other words, contract the abdominals, instead of the hip flexors. Difficult to describe, easier to see!
Decline Sit-up Rocky Style. Do full Situps at a 45 degree or greater angle while throwing a left and a right cross into a training partners hands. The stabilizers are worked more and the punching changes your breathing to put more pressure on your core.
The sprinter sit-up seem to be a fast effective way of killing the abdominal region. You perform it just like the sprinter motion but on you back left knee up & left arm then right knee up & right arm up. The down leg should be straight and slightly off the ground. At the top of the movement you are in a V-up type position with shoulder and part of the lower back off the ground depending on you abdominal strength. You perform this sprint motion as fast as possible with good form.
Vaccum twist is also a good exercise. You sit on a bench with a broom stick across you shoulder and twist slowly while maintaining the thin tummy position. This is great for the transverse abdominals the the external obliques. Using a swiss ball may make this more challenging.
Whenever you work the midsection if is more effective if you use specific exercises to activate all section of the abdominal region.
These are just a few.
Have Fun!
Try to work your entire abdominal area (obliques included) every time. This will keep everything in proportion.
You need a partner on this one. On a decline bench, use a medicine ball and at the top of the sit-up throw it to your partner(who will be standing facing you three or four feet away). He or she will then throw it back to you as you begin the descent. To make the exercise harder, your partner can throw the med ball so you have to catch it with your arms extended further above your head (reducing your leverage). Try to control your descent with your abs as you catch and absorb the impact of the med ball. Then explode back up as you throw the ball back to your partner. This exercise is great for explosiveness, and also works the eccentric portion of the exercise as you try to control the ascent after catching the ball.
Here is a nasty little variation to standard leg raises…
Using straps or holding onto the bar (wmight as well do some grip work while you’re at it) do leg raises (straight legged) all the way up to the bar you’re holding, BUT instead of going straight up add a twist as you’re curling your body to raise your legs to the bar. This will hit not only the front section of your abs but you’re obliques as well. If you can keep your legs completely straight (no knee band at all) I makes it even tougher. Good luck.
Include a day of explosive core exercises in addition to normal ab exercises. (Med ball wood chop, med ball throws, some sledgehammer work)
Although many people hate the Swiss ball, it can be used for many effective ab exercises, like the Sicilian sit-up !
Twist crunch, taking elbow to opposite knee with two second pause at peak of contraction to get the obliques and the upper abs.
Bent knee roll up, lying flat on ground, arms at sides not pressing down for the lower abs.
Dial in the diet and the cardio and you’re ready for the beach!
obviously, usual stuff applies to the abs - if you want em nicer, give em priority; learn about what they do etc.
If your a combatant, or just willing to risk internal damage, try dropping medicine balls (or in the case of one of my more hardcore ex-boxer buddies, have me and another guy throw medicine balls…) onto your abdomen. the smaller lighter balls are great for the obliques, and really get you to tense cuz with that low surface area you learn damn fast that they hurt 
Make sure you fully develop the abdominal muscles - musculature gets pretty complicated down there, and for proportional development theres more than just the Rectus abdominis needs your attention! (uh, when it says “ab tip” if you mean ABdomen then make sure you work your lower back too) - check out IV. Myology. 6d. The Muscles and Fasciæ of the Abdomen. Gray, Henry. 1918. Anatomy of the Human Body. if you wanna boost protein synthesis somewhere behind your eyeballs! or er… however memories are stored. im just guessin its in proteins, all the best stuffs in proteins 
aaaanyway
knowledge lets you better asses your strengths and weaknesses, and understand the difference in muscle recruitment between a sit-up and a crunch!
Anyone whose ever tried Snatch Squats (Snatch (the lift, not the female anatomy, foo’!) the bar and perform squats gettin right down deep) will know how important the abdominal muscles are as fixators - so dont be afraid of stinging them with multi-joint excercises!
Finally, to those in the world with pitifully underdeveloped abdomens, my advice is go easy on stuff involving trunk rotations - you only get one spine, and just like mental health, once its gone, its a fookin’ mare to get back. So until your as stable as a hay-barn wit horses in it (stable. geddit? hehe) dont go takin your spine to the max!
ok i think i used enough exclamation marks for one post!
tra!
My tip:
Superset all abdominal movements; one ‘lower ab’ and one ‘upper ab movement’ like hanging pikes and roman chair sit ups. And after every workout practice vaccuum holds in front of a mirror for 3 sets of your maximum time you can hold it.
A neglected exercise a lot of people forget is breathing. This will train primarily the transverse region of your abs. While it will probably not give you that extremley “ripped” look (which, as has been stated previously, is attained through diet) it will strengthen your tranverse region and decrease the gap most of us have, thus preventing ab and low back injuries to name a few. To breath, take in a big breath through your stomach
muscles, and remember to keep your tounge on the roof of your mouth (this technique will enhance the contraction of your abs when doing any exercise, even crunches!)then breathe out forcefully. For beginners do 5 sets of 5 “breaths” with each breath taking about 5 seconds.
Cheers!
Toss a medicine ball back and forth to a partner on a decline bench. Have the partner toss the ball to either side as well as directly back to you.
Two words: Cable Crunches.
And a few more words:
Twisted cable crunches, and regulars, in a superset, of 4 - 5 sets, twice or three times a week will work magic.
Saxon side bends for the obliques. Good mornings, leg raises on the ground, and hanging leg raises seem to work the rest really well for me. The key for me is to go slow and controlled.
Pavel’s ab book has some useful info if you get past the hype.
Eat better to see your abs. Do heavy compound movements that require good stabilization and then they will be strong.