Voluntear mobile developer, but focus more on web-based skills rather than regular mobile developing skills. The HR will first ask you for your experience, your motivation, and something general; then, he or she will ask you to show him or her your personal project if you have any. After all of these, he or she will ask you if you have mobile developing experience. This step is the most important one since no matter how good you perform in previous steps, if you say you have no experience relating to mobile developing, you will fail.