I've done many long trips on my little Ninja, including a 2,000 mile trip a few summers ago that took me from Dallas to Memphis to Chattanooga, then to Birmingham, New Orleans, Houston, and back home. By that time I'd already been on several trips with 700 mile legs. Here are the main things I've found and done, about myself and my bike:
Myself: Much of what it takes to do long rides is mental and physical, bike prep is actually pretty minor in the scheme of things. Working out comfortable riding positions, and strategies for physical and mental relaxation while still maintaining focus, were a big part of things. It's important to stay hydrated and to maintain a comfortable temperature. I packed a very tall tank bag with water bottles and a folded towel to act as padding, then rested my torso and helmet chin on it, this eliminated fatigue in my abdominal and back muscles. Layers of gear that can be added or removed, gear with vents that can be closed, are good when temperatures will vary a lot during a ride. I rode with a mesh jacket that had a removable thermal liner inside, and a removable textile liner outside. I carried a nice rain jacket that also acted as a wind-breaker. The whole approach was to be as comfortable as possible because that enabled physical relaxation, which in turn prevented fatigue and the need to "power through" bad sensations.
After a few trips I quickly found a good combination of bike modifications. First and foremost I altered the gearing to get the RPMs down below 10K at 70+ mph. I've ended up with a 15 front and a 42 rear sprocket, that has my RPMs below 8K at 70. As you near 10K RPM engine oil consumption really goes up, to the point where I was having to add oil every 1,500 miles or so. Lowering my RPMs at cruising speeds also increased my gas mileage.
The next most important thing I did was to install foam rubber grips. This completely eliminated hand numbness from vibration. The downside was a bit more throttle creep, meaning I have to reposition my hand on the grip to maintain throttle every few minutes, but that movement helps prevent cramping. CycleGear has these grips pretty cheap, and they last a year.
The third thing I did was to get a Corbin saddle. That's not mandatory for long-distance riding, but I lucked into a deal on one a few years back. For riding a few hundred miles a day I don't use it, but if I'm doing a 700 miler I do.
Outside of that, I would recommend adjusting your valves before you start, and if your chain isn't fresh I'd recommend putting a new one on. Check your sprockets to make sure the teeth aren't cupped as that'll trash your chain fast. Get a small can of chain lube and a rag and lube your chain every other tank of gas. Make sure your tires are good, having to replace a worn-out tire mid-trip will be expensive and time-consuming. I like the Kenda K671 Touring tires, they give me a solid 25K miles front, 22K rear, and they're inexpensive. Do all the basic maintenance on the bike before you leave, such as lubing cables, synching and adjusting the carbs, cleaning and oiling the filter, etc. This eliminates concerns and thoughts about those things while riding, which helps with mental fatigue.
And finally, before leaving, give your bike a good washing and detailing. That way when you're done you can admire your trip's worth of bugs and road grime stuck to the front of your bike.
