What skills are most important for me to learn in preparation for a career as a Geologist / Geoscientist?

I'm glad you're choosing geology as your major! Some of my best memories were during my undergrad days hanging out with my geology buds. And it's a great career path! You can find jobs anywhere! In terms of skills that prepare you for a career in geology: that would vary depending on what career path you want to take. I'll give you some advice(in no order whatsoever...I'm spitballing here):

(1) have fun -- The friendships you forge during undergrad will last a lifetime. Don't forget to have fun and hangout with your fellow geos. You're a freshman so you've got 4 years to enjoy yourself.

(2) look for opportunities to do research and present that research at conferences. I'm thinking conferences like GSA & AAPG. Talk to your professors, I'm sure they can help you come up with some question to be answered.

(3) get summer internships !!! -- I can't stress this one enough. In some industries, like the oil industry, it is extremely hard to get a full time job without internship experience

(4) go to a national geology conference -- even if you aren't planning to present, just go to see what is out there. Before I went to GSA I was content with just having fun and getting decent grades in undergrad. I knew that I'd graduate and land an environmental job. But after meeting with grad students from different colleges and seeing all of the research being presented at GSA I knew I wanted to give grad school a shot. And that set me on a path that led me to where I am now.

(5) master the art of presenting -- This is also vital. I give presentations on a daily basis. I HAVE to be good at it or I wouldn't have a job. In my experience: average geologist, great communicator > great geologist, poor communicator.

(6) sell yourself -- this will be an important skill when it comes time for you to get a job. Put a lot of thought into your resume. If you've done research and presented it at conferences, and you've got an internship or two under your belt then your resume will contain things that 90% of the other applicants won't have. Sell yourself during the interview....and make sure you smile a lot. Be friendly. Remember that while they're making sure you're qualified for the position they're also gauging what it would be like to work with you.