Easily my favorite place in the world. Take the beautiful views of the Grand Canyon, the accessibility of Bryce Canyon, and slap them together. You have Zion, the most unique and wonderful place I have ever been.
Camping here is great, but hot, so keep that in mind when you come down. Full hook-ups are available, but you will need to book in advance.
Use caution when hiking in the slot canyons, and flash floods can come at any time (even when there are clear skies, as storms up river can cause them).
Things may seem crowded at first, but the farther along trails you hike, the more alone you will be. Walk through the towering sandstone cliffs and listen to the beautiful calls of the Canyon Wren as you enjoy this incredible marvel of a place.
Some of the trails you don't want to miss, and a short description:
The Narrows: There are two ways to hike the narrows, either top down (which requires either two cars, or a shuttle to take you up early in the morning) or bottom-up. Most folks opt to take River Walk (bottom-up), which begins paved, but will eventually lead you into the river, at which point you hike in/along the river for as far as you like. If you want to go top-down, you will need to obtain a back-country permit. Widely considered one of the best hikes in the world.
Angel's Landing: One of the most Iconic images of Zion, Angel's landing is not a hike for those who are afraid of heights. With narrow ledges and sheer cliffs, you are given only a chain to use as you travel along the trail to the peak of Angel's Landing. But the reward when you get there is one of the best views of the canyon that you will see.
Hidden Canyon: One of the most beautiful hikes in Zion, in my opinion. Similar to Angle's landing, you will be using chains next to a steep cliff, though the distance you are doing this is much shorter. Hidden Canyon offers solitude like no other trail in Zion (if you travel far enough in). If you want to go beyond the normal trail and continue following the wash, you will be doing some small amounts of rock scrambling.
The Subway: Absolutely stunning hike in western Zion, which requires a back country permit. Formations unlike any you will see anyone else. Requires some rappelling to complete the whole trail.
These are only some of the many incredible hikes in Zion, and none of them will disappoint. Please be safe and bring LOTS of water. In the summer time, temperatures in Zion easily break 100 degrees. Luckily, the shade of the canyons offers some respite from the heat. A must-visit park for anyone.