Firstly, you should have a solid experience in writing bots or writing programs, because without any skills in programming it will very difficult for you to write and automated trading bot. Secondly, you should have knowledge in trading activity and you should be a trader, because tendencies always change themselves, so you should know about the present tendencies. Nevertheless, you can pay some money to professional programmists and they will write you a good bot, because it requires a lots of time to do it in case you have little or not knowledge at all.