While I agree with many of the previous posters - change that rear puppy before you leave, don't carry too many clothes (I still overpack after years of LD riding), I do wash clothes in a sink at the end of the day and after wringing them out lay them over lampshades to dry - there are a couple of suggestions I never do.
I never carry much cash. For my last ride, 9K miles to the west coast, I started out with $100 in cash in my pocket and returned with over $80. EVERYBODY take a cc and atms are everywhere I might ride. Even stpping at Mickey D's for coffee in the AM is a CC swipe.
I don't carry a first aid kit. My feeling is if anything really serious happens a first aid kit would only be useful to support my head.
Other than the tool kit that came with the bike I don't carry tools. If the tool kit was more visible I would have removed it long ago. If you plan on riding on roads where your bike might really be nicked up (Dalton Highway) take some duct tape.
I'm not a big fan of the rain but it would never stop me unless it was really terrible (= dangerous to ride in). Snow on the other hand is a completely different matter. After riding through Donner Pass in the snow I can safely say next time I'll wait it out.
As others have noted drink plenty. I usually get some lo cal energy drink or soda at every gas stop.
If you think the weather is going to be chilly then layers of clothes are your friend. When I rode to Alaska I never expected it to be cold in mid August. :dribble: It was 36 one morning in the Yukon Territory. I ended up with a tee shirt, shirt, a sweat shirt, my waterproof jacket liner & my riding jacket. Warm as toast.
Although I never have much of a plan when I start (except some vague idea of a destination), I always have some idea where I am going to end up at the end of a day. By 2 PM I usually am pretty sure and will call ahead to make room reservations. Takes all the pressure off of worrying about not finding a place to stay.
Enjoy the ride!