What I loved most is easily the people and co-workers I met at the NSA, there are so many amazing people there. The second thing I liked the most is the culture, a big thing is to leave your work and career at your location and not mention or take anything home which is very relaxing and prevents overworking. I also really loved the location, Maryland is a beautiful state with plenty of activities and a variety of food. Especially when the food trucks and farmers market stops by, I loved those days.
What I wish was different
My only disappointment I guess were the tours. Like they were cool and gave a sense of how the NSA worked as a whole, but there was nothing linking the NSA to the CIA or FBI or relating to the bigger picture. I feel like I only learned about a puzzle piece in the whole intelligence community. Some more tours relating to other agencies within the intelligence community would have been nice.
For the interview process: When you are applying for this internship you're required to go through a Psych evaluation, polygraph, and operational interview. My advice is to get plenty of sleep the night before and to tell the entire truth. They do not care what you did (as long as you didn't kill anyone or steal too much money or ingest any illegal drugs like weed), instead all the NSA cares about is that you can be truthful. If you tell the truth you're going to be fine (the sleep helps you to formulate your responses). Other than that just be a relatively normal human I guess; don't do drugs or pay for sex (automatic KO).
For the actual job: Always be interested to learn new things and try something different. If you put yourself out there you'll do great. Because really what the NSA is looking for is someone who gels well with the culture and organization as a whole, not a super genius.