Non-CS major applying to CS masters programs

[Notorious QED]

I'm a junior (pure) mathematics and physics double major and I have decided to pursue a masters degree in computer science upon graduation. One of the professors at CMU exposed me to Python during high school, and he basically planted the seed. Taking a course in computational physics last year reinvigorated my love for the computer science and programming, so here I am now! My general question is: what can I do to best set myself up when I start applying to schools next year? 

Here's some background (just so you know what credentials I have as of right now):

• 3.91 GPA
• I've been doing research in particle physics for about a year. Trying very hard to publish before I graduate.
• I will be doing an undergraduate thesis in physics based on this research
• My advisor (full professor, had him for two of my courses) thinks very highly of me and will write me a solid letter of recommendation
• 2 academic awards for physics
• 2 research fellowships

I will be able to complete a computer science minor (and then some) before I graduate. What should I be doing to make my application more attractive? Projects? More coursework? Will my physics research be seen as favorable, or should work a computer science internship instead? Would it be bad if I got my letters of recommendation from math/physics professors and not computer science professors? These questions immediately come to mind, but there are many, many more questions to consider.

Any advice at all would be helpful!