We got a taxi out to the park from the hotel quarter in Brasilia. It cost 50-60 Real and was easy to organise via our hotel reception - they arranged for someone to pick us up at 1630 when the park (allegedly) closes (we saw no sign of anyone leaving at this time).
Entry to the park was 12 Real each - info we could find before varied hugely from 2 to 20 and there is some suggestion it varies depending on if you are Brazilian or not! So go prepared with a bit of cash.
There is a big swimming pool, changing room and toilets. We didn't use the pool as we were here to see some Brazilian animals!
There are a few trails around the park. The shortest one, Capivara, takes you through a forest. We saw lots of birds and butterflies here in the morning (before 10), including two bare-faced Curassows. It took us about 90 minutes with lots of stopping for animals - you could do it much faster.
The longer trail Cristal d’água is split into a few distances, and we opted for the shortest one (5km), given our slow walking speed. This trail goes through proper Serrado. The scenery is great, but it's all flat so no sweeping vistas. We saw hardly any animals on this trail and it took us a really long time (3 hours?). Take lots of water too as there is no shelter anywhere.
As soon as we got to the pool again, lots of wildlife. Hummingbirds, monkeys, agouti's, all kinds of things. So if you want to laze by the pool, don't be afraid of missing out, it seems to be the best spot!