Juniors is basically breaking you down and teaching you how to crawl. They're not trying especially hard to drop people (though they will), but it's more like a haze-fest/introduction. Be loud, be fast, and do exactly what you're told, and you'll be ok. It's easier than seniors, but in my opinion not as enjoyable (I use that word liberally).
Study up on knowledge and customs/courtesies beforehand (I have copies of the Jrs./Srs. knowledge if you want it), and that will save you lots of sleep. Physically Jrs is more cardio-intensive than strength. The longest hike is 6-miles with about 50lbs- not incredibly difficult. Also I'd recommend breaking in boots beforehand, - but that's just general OCS advice.
But basically this is Juniors in a nutshell:
The rules are made up and the points don't matter.