I scheduled a trip to Montana for a conference, and thought I needed to add on a few days to see some of Yellowstone. I knew a guided tour would get me to see the most in the little bit of time I had. I used Yellowstone Alpen Guides/Tours out of West Yellowstone, MT. I did 3 tours in 2 days!
My first tour was the morning mist kayak tour. Turns out, I was the only person scheduled that day! It was a spectacular morning.
My 2nd tour was the evening wildlife tour, essentially driving the upper loop. Connie, our guide that day, was amazing! She was very knowledgeable and great fun. And, with her being the local science teacher for the last 30 years, we got some great science history lessons too.
My 3rd tour was the lower loop, to see all the usual things you would expect to see at Yellowstone, such as the geysers. The weather was perfect. The tour was well-organized, and gave us just enough time to experience the biggest and most popular sites without feeling rushed. Brenda was a great guide, full of information. I particularly loved our stop for lunch at Yellowstone lake; we were the only people there, eating our lunches overlooking the lake and mountains.
When I go back sometime in the winter, I definitely will use them as my guide(s).