Make sure you plan to take a hike to enjoy the back country even just for an hour or so. You will enjoy the park a lot more! Trust me! Maybe even get chased by a Buffalo! fun stuff! heh!
So, make sure you bring good shoes, water, and sunscreen.

Yellowstone National Park - Admission. If you are a Senior Citizen or have one with you they can buy the park pass that can be used to lower your costs at National Parks. Wildife can be viewed at a distance and I have some great shots. Keep your eyes open as they can be anywhere. If you are the first to spot them then you have the best chance for good pictures before other people notice. People will try and get as close as possible to the wildlife and when the wildlife moves deeper into the park the people tend to move in closer. Thus you will sometimes lose great pics as people don't know how to stay at a distance. CAUTION: Feeding of the wildlife is done which is against FEDERAL LAW. You Will Be Dealt With If Caught and SEVERELY. This has caused numerous wildlife to be destroyed and people being hurt or killed due to this ignorance. You will see plenty of elk, bison, deer, fox, coyote, etc. Take plenty of pictures as the views are magnificent. Food and giftshops are found in the park as well as a post office. The park really needs a few days to see it all. You cannot see it all in one day. Old Faithful - There are a lot of seats and basically anywhere the seats are you have a good view. However if you want to sit you need to get there either early before the eruption or sit there a while until the next. There are quiet a few geysers just not as spectacular elsewhere in the park. Also there are quiet a few boiling mud pits around as well. CAUTION: STAY ON THE WALKWAYS/PATHS. There have been a lot of people falling through the very then crust around some of the geysers and mud pits and either have been scalded or died due to negligence. You will be near heat but it usually isn't to hot as you will feel breezes usually to help with that. Also expect to smell sulfer sometimes very slightly to enough to almost take your breath away. Most of the walkways are wheelchair accessible.

Visit Old Faithful and the surrounding geysers is a must in the area. The smell of sulphur can be overwhelming at times but you get used to it. The boardwalks make most walks to see other geyers and mudpots very manageable for most people. There are buffalo everywhere but remember they are wild, as are the elk, that are also very plentiful.