Your core is the makeup of muscles that support your stomach muscles and protect your spine. Besides getting that shredded look, it's a good idea to have a strong center that will enable you to have better performance in the gym, on the court, on the beach, and during everyday activities.
HOLD THE PLANK
Some great core exercises you can add are the everyday plank hold exercise. This can be done on your hands and elbows. Hold a plank for about 30-60 secs at least 3x during your normal workout routine. So, for instance, if you workout for 45-60 mins, do a plank hold for 30-60 secs at the 15th, 30th and 45th min of your routine.
If you're the weekend warrior and you want to step your game up, do the plank hold on your hands either on 1 leg at a time or on a stability ball for 1-2 min (each leg if doing single leg holds). This will up the ante for you and get your inner core muscles to fire off like you've never felt before! Also do this at least 3x during your normal routine.
That's 3 plank holds that will get your core challenged and feeling tighter and stronger within weeks. Do this at least 4-6 weeks and watch the difference you see and feel.