Luggage and bags:
This being one of the top backpacking destinations in the US, a backpack might be a good thing to bring along. There is such a big network of trails, you just couldn't see them all day-hiking so you'll need to carry all your gear...you guessd it, on your back. A day hiking pack is also necessary if you don't plan on backpacking. Even if you're not spending the night, you need to carry clothes for changes in the weather, ample snacks for energy and plenty of water.
Clothing/Shoes/Weather Gear: Good hiking boots are something not to skimp on at this rugged park. They provide the ankle support you need and protect your feet from injury as well as allowing you to traverse more miles in comfort. Good quality socks are something people tend to forget but they are just as important as boots if you are walking long distances. Liner socks fit inside these and help reduce the chance of getting blisters. While shorts are fine for hiking, long light pants give you more protection from bugs, scratches and the sun. The same thing goes with shirts. With the new materials that hiking clothes are made of, there's no need for a shirt with long sleeves to be hot. When hiking at elevation, you should always carry some warm clothes in case there is a weather change which is always possible, even in summer. A fleece, warm hat, and rain jacket are the bare minimums for safe hiking.
Toiletries and Medical Supplies: Bug juice and sunscreen cannot be overestimated.
Photo Equipment: A wide angle lens is the key to great landscape photos so you can bring some of the foreground into your photos to make them more interesting. A good quality zoom makes for great shots of the wildlife without infringing on their space.
Camping/Beach/Outdoor Gear: A good quality tent is money well spent. Think of the money you save on rooms and it's paid off quickly. Add to this, you can hike and camp to places not possible without. When you are that far from civilization, the last thing you want is a leak so put out a few more dollars and get the protection you need. The same thing goes for sleeping bags and mats. The latter especially cannot be overestimated. They not only provide comfort, they insulate you from the cold. You can go without cooked food for a day or two but a light weight stove allows you to add variety to your meals and to have hot beverages, something that might not only be nice but a life saver if you lose core body heat.
Miscellaneous: A great hiking partner is invaluable. It's safer not to hike alone and a lot more fun when you have someone to share all the beauty with. Thanks, D for being the perfect one.
You will definitely need hiking shoes, which are a necessity on the park's 800+ miles of trails. You may want to bring rain gear, although summer thunderstorms in the Sierra are short and generally won't get you too wet; however, waterfalls like Vernal and Wapama Falls might.
Photo Equipment: Bring a tripod (I didn't), so you can catch the beauty of Yosemite after dark.
Camping/Beach/Outdoor Gear: Weather in Yosemite is unpredictable, so be prepared for both freezing and scorching temperatures. Be sure to bring sunscreen (essential, especially on the Wapama Fall Trail and Tioga Rd). Also, pack mosquito repellent to ward off the billions of Yosemite mosquitoes. If you're staying at Curry Village, pack a flashlight.
Luggage and bags:
* Map and guidebook;
* 2 Liter of water;
* Fruit / power bars.
Clothing/Shoes/Weather Gear: * Hiking boots;
* 1 extra t-shirt;
* Shorts with many pockets;
* Fleece type jacket;
* Hat / cap;
Toiletries and Medical Supplies: * Lip balm;
* (Neck) sunblock;
Photo Equipment: * Camera and lots of films!
* Extra batteries;
* Lens 210 mm.
Miscellaneous: * Binocular;
Clothing/Shoes/Weather Gear: Bring warm clothes, particularly if you are going up to Glacier Point or the Tioga Road, which are at higher altitudes where it is noticably colder. During our four days in the park, the temperature in Yosemite Valley was in the 70s and 80s, while it was in the 50s up on Tioga Road.
For hiking, make sure you wear comfortable shoes, shorts, a t-shirt, and bring a sweater in case it gets cold. In October, it was quite warm and I was happy to only be in shorts and a t-shirt. However, if it had gotten cold, it could have been a long hike back to the warmth of shelter.
Toiletries and Medical Supplies: Mosquito repellent, sun screen and band aids are very helpful at different times of year. The band aids in case you get a blister or scratch, of course.
Camping/Beach/Outdoor Gear: Bring towels for swimming, or for drying off after washing if you stay at the camps.
Even when the summer is hot, the evenings can be pretty cool and also the drive in the touristtrain is windy (because of the speed). A warm jacket is a good solution.
Photo Equipment: Twice as much films then you think you will need.
Camping/Beach/Outdoor Gear: If your going hiking you need very good hiking shoes. If your going with a tent, camping-equipment is a must and vacuum-packed food/drink as well (bear-proove stuff!). Climbing-adventures need - of course - a whole different set of equipment.