Decide on a focus in theology. Ask yourself if you feel a call to pastor or to teach theology at a seminary. Plan your studies accordingly.
Have a conversation with the set leader of your congregation--your pastor, rector, imam, or rabbi. Explain to him why you feel that God has called you to a life of ministry.
Check the requirements of your religious institution. Go to the website for the denomination, or speak with your minister. There may be requirements to go to a seminary to study for a degree.
Find out how much it is going to cost to attend. Ask your religious institution if it will sponsor you.
Present all necessary paperwork to the leader of your congregation. This includes the results of a criminal background check, credit check, or anything else that gives your set leader a picture of your overall character.
Ask him to write you a letter of recommendation. Also, make requests of other prior ministers or leaders under whom you have served. This gives the seminary to which you are applying a wider picture of your character, commitment to the ideals of your faith. Also, asking multiple members of the clergy will give you a cushion in case your leader feels uncomfortable recommending you, for whatever reason.
Research the seminaries within your faith. Browse the Internet. Whether your seminary of choice is on-ground or online, ask two major questions--whether it is accredited, and if former students have posted complaints with the Better Business Bureau regarding that institution.
Find a mentor, or form a relationship with the one your sponsoring congregation, or the seminary, will assign you. Observe this successful religious leader, or theology professor in action. Take many notes. Watch carefully how he organizes and delivers his sermons-- or classroom lectures, if he is a theology teacher. Pay attention to how he deals with his congregation members, or students, if he happens to be a seminary professor.
Write papers that require you to think about a deeper exegesis of the scriptures of the primary holy book of your faith. Do work in this area beyond what your professors require you to do in class.
Practice lecturing or preaching on a given topic. Use a tape recorder, and speak on topics you have written about in your papers. Have your mentor, or other students critique you on such areas as presentation, exegesis, and voice quality--whether you varied it often, or spoke in a monotone.