1) Planning is key when choosing a mobile app development company. It is important to set clear timelines and budgets to avoid delays and wasted resources. 2) Lack of proper project planning and budgeting are common mistakes made during mobile app development. Companies should account for factors like the app's scope, features, and audience when setting timelines and budgets. 3) Not staying involved throughout the development process is another issue. Regular communication between clients and developers through meetings and feedback ensures issues are caught early.