Internship Preparation / Timeline?

I have just started my junior year of college at a target / semi-target. I'm wondering what I should be doing between now and interview time in January. I'm interested in I-Banking / Consulting. Do I need to choose which area I want to focus on now, or can I apply to both with relative ease?

Should I be purchasing interview prep books? If so, which ones are good?

I'm just not sure what I should be doing to make the best use of my time between now and application time. Additionally, looking for advice on the best ways to prepare for interviews, applications, etc

As for my credentials, I have a good GPA (3.8+). My work experience is o.k., I had a paid research assistant position for a finance professor over the summer in the M&A field. I'm also trying to figure out what I should aim for in terms of internships. I'm kind of clueless of this process.

Thanks