When choosing an ecommerce store development agency, start by assessing their experience and expertise in ecommerce development, particularly with the platforms you're considering. Review their portfolio to gauge the quality of their work and see if they've successfully executed projects similar to yours. Look for agencies that offer comprehensive services, including design, development, optimization, and ongoing support. Consider their communication style, project management approach, and ability to understand and meet your specific business needs. Request proposals and quotes from multiple agencies to compare their offerings and pricing structures. Ultimately, choose an agency that not only has the technical skills but also aligns with your business goals and values, fostering a productive and successful partnership.