Yes's and no's. Lie on your back and nod your head (this would be the "yes") and no's are done on your stomach bringing your head up. You can also tilt your head right and left when your bring it up. These should strengthen your neck
When you do the nodding yes like cardstars said remember to not move anything but ur head and nod until ur chin touches your chest and all the way back repeat it. Also you can add in the sides by nodding till ur chin touches ur chest then slowly moving ur head as ur chin is touching ur chest all the way to your right then all the way to ur left and then down, and repeat it as many times as you think you can comfortably at your current level of strength. Neck bridges are also a good exercise for neck strength.
