If a cymbal is not played correctly it may crack.. But you can reduce the potential risk of cracking by choosing the right weight, size, and positioning for your needs.
What you can do to protect your cymbals are:
Choose right cymbals
Hitting hardly to a small or thin cymbal won't help to get a big sound and volume due to its strength and limitation. Do not use use small and thin cymbals for high-volume settings, unless you need a contrast in your entire set-up. Don't forget that they are not as durable as the heavy ones. For volume and durability, go for the big and heavy models. It would be a good decision to consider bright and powerful sounding cymbals, such as MetalShop, PunkHead, T-Xtra and T-Alternative. Low pitched cymbals like Cymbalmaker, La Pasion Turca, T-Natural and T-Classic etc.
Pay attention to your stands
Be sure that the metal of the stand doesn't hurt the cymbal. Use a nylon tube over the center rod.
Use a felt on top of the metal washer under the cymbal. Pay attention to prevent metal to metal contact.
Use a felt on top of the cymbal
Pay attention to wing nut tightens. Not to loose, not to tight.
Use smaller felts especially on hi-hats.
Do not over tighten the cymbal
Don't forget that vibrations generate the sound in the cymbal. To achieve a better sound, loosen your cymbals and give them space to vibrate. Over-tightening a cymbal will kill its sound. It won't vibrate enough and produce a sound as dampened by a piece of tape. Playing an over-tightened cymbal will cause to much pressure and creates a stress in the metal, this may end up by cracking. Usually around the base of the bell or straight from the edge.
Pay attention not to over angle crash cymbals
If the angle of the cymbal is too steepy, then there would be an extra pressure which may end up by cracking. At this kind of playing situations position the cymbals fairly flat and give an angle towards yourself. Pay attention at tightening the cymbal.
Play your crash cymbals correctly
The edge of the cymbal is meant to be 'crashed', but there are two things you can do to get the most and best sound out of your crashes plus avoid cracking them:
Don't hit directly into the edge. Hitting directly to the edge may cause a harm both at your stick and your cymbal. You won't be able to get the perfect sound because the cymbal won't vibrate in control. Striking and pulling back will be the best way at these kind of musical needs.
Glancing strokes will make the cymbal move freely and the vibrations will be in control which will cause a better sound. These kinds of strokes will be more satisfactory since the stick is on an off the cymbal before the vibration. This will end up by a smooth sounds and you will be able to get the best out of your cymbal.
Protect Your Cymbals
Bu sure that your cymbals are safe after they are off their stands. Avoid leaving your cymbals out of their bags or cases ( a small nick may be a bigger crack)
Use quality cymbal bags or hard-shell cases to store and carry your cymbals.
Insert dividers between your cymbals such as clothes, towels, plastic bags etc. to prevent contact.Stack your cymbals and fit small ones into larger sizes.