Having graduated from seminary (and observed many others), I agree with much of FatherGiryus' advice. I would put it in this order of importance:
1) Be married to a practicing Orthodox Christian already, or have strong prospects of such a marriage (hopefully leading to an actual marriage while still a seminarian).
There are many reasons for this: Your wife/family gets to grow into your new role with you; you have a more mature marriage; you're no longer in single student mode, but now a family man with responsibilities; and, quite practically, you are actually able to be ordained upon graduation. Quite often, unmarried men graduate with debt and without great job prospects until they can find a bride and get ordained.
2) Know the realities of pastoral life. People are attracted to the priesthood b/c they want to be a liturgist, preacher and teacher. Equally as important (and more time consuming) is your identity as head of a clerical family (with its unique pressures); pastoral care giver; manager of church staff; non-profit executive (fundraising, coordinating volunteers, leading meetings); "public person" (member of community organizations, local charities, diocesan groups, etc.). If you're in a jurisdiction that doesn't have a policy of paying full-time priests a living wage (sufficient to raise a family on), then all of these issues get even more complicated.
3) Have experience outside of being a (liberal arts) student. Fr's suggestion is to go to grad school and get MFT licensure. Aside from (a) putting you further into debt and (b) keeping you in "student" mode, it's not a bad idea. If it's a passion, go for it. Otherwise, I would say the essential goal is to gain knowledge of human beings (perhaps even how the real world works) and have skills that might actually provide you with an income when needed. There are many ways to do that, the most effective way being to get a full-time, entry-level job. You'll learn plenty about dealing with people -- and have something to put on your resume -- if you enter the workforce. Also, not a bad way to learn about what life is like for most of your future flock (balancing work, family and church as a lay person).
Btw, I went to seminary right out of undergrad. Got married half way through and worked while still a student.