Tips on being prepared for UMD CS? Will be a freshman in August

Hey guys! I will be coming to UMD in the fall as a freshman under the major of Computer Science. After speaking to some current students, I understand that the program is by no means easy, and would definitely like to have some sort of a head start before classes begin. I've done a basic Java class, and mainly just have the ability to write up some simple programs and commands. I also understand that there are many people that do come in without prior knowledge, however from what I've heard many of them aren't exactly prepared to be a CS student. If any current students could give me any advice/tips on what to specifically be thorough with before classes start in the Fall, it would be greatly appreciated. I plan on learning a bit more Java so that the basic classes in Freshman year flow more smoothly.

TL;DR - How much prior programming/CS knowledge is beneficial before starting Freshman year as a CS Major?