Mark your left & right shoe with permanent marker.
Get professionally fit every 3 months even if you don't think you need new shoes. You may not but the right shoe and fit is vital.
It is normal & very common to have 2 different size feet & since pointe shoes are not foot specific, purchase 2 sizes and you'll have 2 pair of shoes!
Keep your shoes in a mesh bag. After dancing be sure they are not left in your closed dance bag - they need to air! Perspiration will break down the box.
Don't leave shoes in a hot car. Climate & humidity play a huge role in the life of pointe shoes.
Keep toenails short.
Convertible tights are best so that you have access to your feet.
Be bunion cautious! If you see any signs I suggest a Spacer which fits between the big and 2nd toe.
Toe Pads are discretionary - some instructors don't allow pads. Proper pads will increase comfort and cut down on blisters and sores.
Its time for new shoes when the shank becomes too flexible or breaks and/or the platform or box becomes very soft. It's typical for growing dancers to outgrow their shoes verses wearing them out.
Happy Dancing!