Look for contractors with expertise in cross-platform app development. A business focused on native app development won’t have the skills needed to make a cross platform app. Keep in mind that the company has relevant expertise — both in working with businesses of your size and in your niche. They’ll know what pitfalls to avoid to make a solid product. This is where a portfolio can help — you’ll be able to find out whether any of projects similar to you have turned out a success. Finally, make sure that the company has talented developers. This way, you won’t have to overpay for development mistakes. You can read more about factors which influence whether the company is good.