I'm very interested in trying to get published as a history major in order to ease my path towards becoming a history professor, so I've been thinking about trying to do research on my own. As a result, I want to get published before I graduate but I hear it's not easy to get published in regular journals so I was thinking I should get published in try an undergraduate journal instead. Would that be a better alternative or no? If not, what are some tips to getting published in a regular journal?
First of all, if you've already written an excellent paper of which you are proud of, then why not submit it to an undergraduate history publication? It certainly won't hurt your chances for graduate school admissions. In fact, I would say that it certainly demonstrates interest and willingness to engage in the academic community of your chosen field. This is something that graduate admissions look for and care about when they're evaluating your application.
Undergraduate publishing opportunities are quite plentiful, and many of them are becoming very well-recognized. In my opinion, I've found that the writing/research published in the best history journals are neck-to-neck with papers that could pass a graduate thesis defense.
I would encourage you to check out: http://history.unc.edu/undergraduate-program/undergraduate-journals/ with an emphasis on Yale's and Vanderbilt's undergraduate (which are one of the few journals open to undergrads from all universities rather than just serving their own university/college). (Full disclosure, I am an editor of the latter, see: http://vanderbilthistoricalreview.com)
Publishing as an undergrad is a good idea. In particular you might want to publish something related to your undergraduate honors thesis. The Journal of Young Investigarors is a good choice. Several undergrads from projects I have been associated with have published there. If you are serious about being a History Professor, a publication (and an honors thesis) will help you get into a good graduate program, and will show that you are serious about gaining the experience needed to succeed in academics.
Don't waste your time. Publications in undergraduate journals don't count for anything except demonstrating your interest in the subject. It is better to spend the time really polishing a good writing sample and cultivating letters of reference from your professors. (As well as keeping your grades high.)
EDIT: Publication in an undergrad journal won't realistically help polish the writing sample. Other undergraduates will be the referees and editors involved with the process. It would be far better to take the piece to faculty members, and say that one wants to use the piece as a writing sample and solicit professional feedback rather than student feedback.
Also, you absolutely need to look hard at the placement numbers for any graduate program you want to attend. It is much better to simply pursue a non-academic career right away rather than spend 5-8 years in graduate school only to find at the end that you have no realistic hope of getting an academic job anyway.
(To contextualize my advice, my area is Philosophy and I'm located in the US.)