Oh, Disneyland... every little kid's fantasy world. How I wanted to visit here so badly as a child, meet all my favorite Disney characters, see the parade, the famous Disney castle... but sadly I never got the chance to go until I was an adult. That being said, even adults can have a ton of fun here! I'm sure my preferences would have been different as a child, but as an adult, I'd have to say that the best part of the entire resort is the Adventureland Park. Amazing rides, if you're into that sort of thing. Of course there is so much to see and do in the entire resort, that you really can get stressed out thinking about how you'll see and do it all. Several days to spend in all the different parks is a must. If you want to spend a little extra money, it can definitely be worth it to even high a professional trip planner to help you out with all the tricks and tips you would have a hard time finding out about on your own. Buying a Fastpass if definitely worth the extra cost, because if you don't, you can easily spend much of your time just waiting in lines! And seriously, get there early, right when the park opens (at 8am in the summer), and hit all of the most popular attractions then. Don't skip the Indiana Jones ride, it's amazing! But get there first thing in the morning!
The Fisherman's Wharf is definitely a bit heavy on the tourist side of things, but it's still worth seeing and enjoying. Of course prices tend to be a bit high due to the tourist factor, but there a lots of options for good food, and of course lots of touristy swag to buy. My favorite part of the experience is going to see the sea lions that hang out on Pier 39, in an area that has been set aside for them. Very entertaining! However, they are not always present because like many wild animals, they have their own schedules and migrations to stick to, so it's a good idea to do a quick check online before you go if that's mainly what you are going to see. There are also really great views of Alcatraz, and you can sign up to take a tour to visit Alcatraz, which is one of those classic American things you've got to do at some point in your life. Parking in the area can be a bit difficult an pricey though, so it can be worth it to park a little farther a way and either take a nice walk through the vibrant surrounding SF neighborhoods, or take a cab if you're a little farther away.
I've been the the Las Vegas Strip several times, and I have to say that I have mixed feelings about my experiences there. On the one hand, there is so much to do and see, the party never really stops no matter what time of day it is, and it's easy to get swept up in the excitement. However, there tend to be a lot of drunk, stupid, and annoying people walking around at any given time, which can really ruin your mood if you let it. But, this does make for some very fun people watching! The Strip really is quite long and intense, so I'd recommend not trying to take it all in in one day or night. A good plan of action is to walk a little ways, then duck into any given casino for a few games, and to remember that you get free drinks while you're playing, even if you're playing a cheap game, so do take advantage! It's easy to spend a lot of money very quick while in Vegas, but if you're smart about it, you can have a pretty cheap trip. A word of advice, if any locals on the street approach you offering to give away any coupons, flyers, tours, or "free" admissions to shows or clubs, it's best to just ignore them or say "no thanks" and walk away, because once they give you their "free advice" and coupons, they insist on tips and will hound you for blocks yelling at you if you refuse. And if you want to take picture with the various street performers, it's good form to give them a small tip too.
The Great Smoky Mountains National park is a beautiful example of America's astounding natural scenery. Although there really isn't a bad time of year to visit, I would highly recommend visiting in the fall when the trees start to change. The fall colors are amazing, and you really feel like you are stepping back in history to a time when this country was less populated and more natural and wild. You can enjoy just a day trip driving through and taking in the natural beauty from your car, or you could easily spend several days camping and exploring some of the hidden gems of the park. If you really want to get the full sense of the majesty of the park, I'd recommend visiting the observation tower at Clingmans Dome, which is the highest point in the park. Stunning views! There is even a paved path that is a relatively easy hike. Cades Cove is also definitely worth visiting, with many historical log cabins, barns, churches, and other buildings.