Strengthen the legs not just the feet. Strong legs are equally important when trying to improve the point of your foot. The legs allow you to lift up and outward which allows for a better point and on pointe technique.
Improve your turnout. Rotating the legs outward from the hip is called turnout. Dancers have varying degrees of turnout ability. Improving the turnout will free up the foot allowing you to point more freely. Stretching can also help improve turnout.
Invest in the proper pointe shoes. Have your shoes fitted by a professional and do not attempt to go en pointe unless you have had the proper training and evaluation by your instructor. You should go in person to get fitted. Once you have found the correct pair, bring them to your instructor for inspection.
Know your foot! Everyone's feet have different characteristics and depending on those traits, you may have to make adjustments in your training to achieve a better en pointe technique. Low arches or short toes may require specific pointe shoes to help shape and support the foot. While there isn't much you can do to physically change the shape of the foot, hard work and the right shoe can improve the appearance of your point.