I mean to say, what skills and topics should a historian possess, beyond history specifically? Is it an absolute necessity that a historian who specializes in roman history speak Latin fluently in order to be a credible source, or is intensive study of translated documents (still firsthand) and possession of a PHD enough to give their statements and interpretations the backing necessary for discussion? I apologize for how broad the question is, I'm starting my first year of university next year (as a history double major) and am unsure what electives I should be taking to help me better understand my field and help me out later on; any languages I should learn, regardless of my field?
Write write write write. The only method you'll have to express your intelligence academically is the writing you turn in. Make sure to pay extremely close attention in your English gen eds. Also, actually reading makes it easier. It's unlikely that you'll actually complete every book assigned to you. When you can't, you have to rely on your writing skills to be able to extrapolate more from limited content.
Also, your professors are going to hammer into you the idea of contingency. Understand that history cannot accurately be perceived in retrospect. It's totally necessary to detach yourself from preconceived notions and general assumptions. When you do that, you'll get to the ideas that blow your professors out of the water.
I'm not a "certificated" historian, I call myself a researcher mostly. However, I do a lot of the same functions so I'm going to throw out a couple of points.
Curiosity and perseverance/patience are two top items. I do the research because I am curious and want to learn at a deeper level than just reference books. The desire to do that drives a lot of the other skills - it's a benefit to learn the US Navy 1941 filing manual to find documents at the US National Archives? OK, I'll sit down for a couple of nights and design a reference system for myself to handle the things I can't outright memorize.
The discipline(s) you settle on will drive a lot of the specializations you need, but keeping yourself curious will go a long way towards keeping it an activity you want to do long term.
You may want to check out this section of the wiki for previous answers that may be of interest to you.
In regards to your language question: a professional historian will generally want to learn the relevant languages to their area of study. One can't necessarily learn all languages, but if a particular source is going to form the basis of whatever you're writing then it's more important to be able to analyse it in its original language.
That's not to say language barriers can stop you from studying non-English language areas of history, but your focus might have to shift. For example, if you wrote about British policy in China then you could build the foundation of your work on English sources.
The main skill of an historian is, in short, being able to take a variety of sources and build them into a coherent argument, so any class that uses similar skills would be useful. If your university offers a course on historiography then I would highly recommend you take it.
For a general introduction to historical methods I recommend either Writing History: Theory and Practice by Kevin Passmore et al or History in Practice by L. Jordanovna.