I'm not in the service but I'm pretty much ready to go on a 1200 mile thru hike of the Pacific Northwest Trail from Glacier National Park , MT until I plunge myself into the Pacific Ocean. I have all my tickets and permits and my Amtrak to East Glacier where I am planning to add an extra 110 miles to my ruck to the Chief Mountain Custom USA-Canada border to begin my trek from the official start of the PNT! I'm an ultra light backpacker and my baseweight in 14 pounds and with food and water and fuel I am sitting around 22-23 pounds with some luxury items (projector, iPad, and bluetooth speaker - sex appeal in the fire lookout baby, it's movie night).
No one cares. Seriously. "I do a lot of hiking, this is what works for me" or a similarly bland intro to this thread would work. This reads like some blowhard, know-it-all opinion we've seen dozens and dozens of times before. Ask yourself this: would you walk up to a complete stranger and drop that paragraph on them? If someone did that to you would wait for them to finish before laughing or walking off
Backpacker basics: Proper fitting boots. Proper fitting clothes (nothing cotton). TOE SOCKS!!! INJINI OR DARN TOUGH OR SMARTWOOL!!! Prevents blisters in between toes... Us marathoners know what's up! Proper fitting backpack. Make sure it's packed right... light stuff like sleeping pad and clothes or whatever at the bottom, then medium heavy in the center (I typically put my whole sleep systems in a waterproof bag, and then whatever you wanna quick grab at the top. Since you're a Marine you need a backpack with a frame that can support at least 80-100lbs. Make sure it fits close to your body and use the load levelers if you can. Also put the bag on properly too. If you have REI nearby ask them to help you if you don't already know, but I like to start with my shoulder straps, then chest, then belt buckle, and load levelers if I have them.
Good, basic info. You're hiking, not rucking, but those basics are solid...and we veterans know what's up! (See how that sounds?) Then you flame out and blow a fiery crater into the planet:
Since you're a Marine you need a backpack with a frame that can support at least 80-100lbs.
You probably have no idea how insulting it is to read that. If you haven't worn a uniform then it is a bit presumptuous to tell someone who IS in uniform what they need for rucking of all things. I understand your intent, and that you mean well, but c'mon. That kind of stuff will turn people off. Quickly.
Run a lot. A LOT! As fast as you can as many times a week as you can without injury. Take a week off every third or fourth week) and Swim a lot too! I really love women's aerobics aka: crossfag. It's usually between Barre and Booty Pump or Zumba, but if you can get into Booty / Body Pump it's the best. Have you ever done 60 minutes of non stop squats and lunges with 60-100 pounds? Trust me these women have and they could break 90% of men's necks with the techniques coming out their buttcheeks. They rock it on the trail! I've been checked in half marathon Spartan Races by women rucking uphill with 40lbs and they are like "This is what carrying a child helps you do!"
Presentation matters and without us knowing you, this sounds stupid. Good intent, good info, but a horrible way to express yourself to people who know nothing about you on a topic where we literally have experts.
The best thing though is simply to ruck. Move as fast as you can up the steepest mountains you can. I live in Seattle so the best mountains in the country are basically all around me so I'm lucky but I mean... If you're in New York or something try and goto some tall buildings and use their stairwells... Empire State would be a dope race to the top in all your gear. Try not to pass out. Best of ruck (LOL!) to you in all your endeavors!
And their un-arthritic knees and spines always need more conditioning. 
