I'm excited, the first challenge is at 12 noon my local time. I plan to get to my favorite farming spot that I can ride my bike in a 2km loop while spinning 18 poke stops and 4 gyms and start playing a little before the first global challenge. Challenge two starts at 2pm for me. Unless I have to change locations because say a certain type of Pokemon wasn't spawning at my good farming spot I'll still be there when challenge two starts at 2pm. After its over at 2:30 if my phone isn't overheated already I'll need to recharge my phone and portable charger as well as feed myself some berries. After food and a recharge for the technology I plan to go to 1 of 3 parks downtown for challenge three at 4pm. Then from 4:30pm onward the challenge is to talk to/meet as many trainers as possible in order to form the strongest raid team possible to be ready for what ever the Mystery Challenge may be come 6pm my local time!
Footnote: First 3 Global challenges last for 30 minutes; Mystery Challenge's duration is 1 hour.