At minimum, you need one 12" x 12" (31cm x 31cm) nest for every four to five hens. Too few nests or small nests can cause eggs to be trampled or squashed and broken, or can stress the birds and lead to more pecking. You want to reduce the chances of a broken egg as much as possible so the chickens never get a taste for them.  Nests should be at least two feet (61cm) off the ground, and four feet (1.22 m) from roosts.  Remove any broody hens (hens that insist on sitting on their eggs to hatch them) from the nesting area so they don't occupy valuable nesting space and contribute to higher traffic in the other nests.  Consider a nest designed to allow the eggs to roll away into a tray after the hens stand up, keeping them safe from pecking and getting stepped on and broken. Bright lights will stress out your hens and make them nervous, which increases pecking. Turn the nest box away from the opening of the coop and away from the direct sunlight and don't install bright lights. You may need to cover any skylights or windows to create a more comfortable environment.  Remove anything that creates loud noises or sudden movements, as this can frighten the hens. If they get scared and run from the nesting box, they may break the eggs.  Reducing light sources can also help keep the coop at a comfortable temperature--if it becomes too hot, the chickens can get irritable and start pecking more. Make sure each nest has a few inches of clean, dry nesting material (such as wheat straw) at all times. If you can keep the eggs from accidentally breaking (by knocking into each other in the nest or being laid onto a hard, unpadded surface), your hens will not have the opportunity to learn how tasty eggs can be. If an egg breaks in the nest, quickly clean out all the soiled nesting material. A bored and irritated hen is more likely to start pecking, so make sure they have plenty to do. Hang a cabbage for them to peck at and give them adequate space to walk around and exercise.  Try to set up an area where they can roam and climb...

TL;DR in Indonesian:
Kurangi kerusakan telur dengan cara mencegah sarang agar tidak terlalu padat. Buatlah area bersarang yang gelap dan hening. Sediakan material bersarang yang cukup untuk melindungi telur-telur yang baru keluar. Jangan biarkan ayam Anda merasa bosan.