This is probably the most popular option for tourists visiting the west block, though not necessarily the best or most rewarding. The ecotour is essentially an interpretive trail that you can drive along. It takes you on the main road through the park, with interpretive stops along the way. The main highlight of the tour is the prairie dog town, where you may also see the endangered burrowing owl if you're lucky; however, there are several interesting stops along the drive, as well as pretty views as you move from uplands to the valley bottom.
Be sure to purchase the self-guiding brochure (~$2) because there are no interpretive signs at the stops. Although the park map suggests that the ecotour route loops back around to Val Marie after exiting the west end of the park, the brochure advises you to stay within park boundaries - and for good reason! I've done the full loop, and I can tell you that you aren't missing anything. It's just a long gravel road through private farm lands, which you'll have already seen a lot of on the way to the park! Just double back the way you came and maybe you'll see something you didn't see on the way out, like a herd of bison, a rattlesnake, a short-horned lizard, a burrowing owl...
While I do recommend taking the ecotour, I also recommend doing at least one hike in the west block to get a full appreciation of the beauty and vastness of the park. The ecotour is a great starting point.
The view from the trailhead, where the two trees stand, is a great photo opportunity. You know you're in the prairies when trees serve as landmarks! The trail itself offers some pleasant views, but I highly recommend purchasing the self-guiding brochure to make it worthwhile ($1 or $2) because there aren't interpretive signs along the trail, only numbers corresponding to those in the brochure. We went not knowing about the brochure and turned back after a short way because the view is fairly uniform along the trail and we were missing out on all the interesting tidbits of information (plus we were short on time).
If you only have time for one trail in the West Block, do the 70 mile butte. It's relatively short and goes in a loop, so you don't have to backtrack. This trail offers beautifully expansive views of the Frenchman River valley. Keep an eye out for rock wrens - funny little bobbing birds - and, if you're lucky, bison!
The park roads can become impassable after heavy rain, and the park advises visitors to exit immediately when possible. Obviously we can't predict the weather, but check the forecast before heading out and/or call the park to check the road conditions to save yourself the disappointment of driving all the way out there only to be denied entry or to have your trip cut short.
Luggage and bags:
A backpack with good support if you're hiking.
Clothing/Shoes/Weather Gear: Proper hiking shoes, not sandals (cactus, possibly rattlesnakes); pants better than shorts (one species of cactus "jumps" onto your calves as you brush against it!); long-sleeved shirt if you burn easily; wide-brimmed hat; lots of sunblock (prairie sun is intense!); lots of water - there are no facilities in the park; snacks.
Toiletries and Medical Supplies: A first aid kit is always a good idea.
Photo Equipment: There are lots of photo opportunities at the park. Greater zoom capabilities = better chance of capturing wildlife since the open prairie makes sneaking up on anything very difficult! But don't despair, there are many beautiful landscape photo opportunities as well.
Camping/Beach/Outdoor Gear: If you are camping, bring everything you have. Camping is strictly rustic within the park. No open fires permited.
Miscellaneous: Field guides - especially birds and wildflowers. Binoculars.