New Theory: 10th Pokestop Bonus
A Reddit user has found, and many others have confirmed, a neat way to earn more items and XP at Pokestops.
Apparently, on your 10th Pokestop visit, as long as all 10 Pokestops are different, you’ll be rewarded with 6+ items and 100 XP. You’re also guaranteed to get an egg on this 10th visit.
There are some caveats that go with this bonus, the most important of which is that you can’t have visited any the 10 Pokestops in this “bonus chain” within the last 30 minutes, and that you don’t wait more than 10 minutes between visiting any two Pokestops (otherwise, the counter gets reset and you’ll have to start the chain again).
Note that you can get the double items and XP bonus at any Pokestop at any time in a random fashion, but the reported method above is the only way to force it to happen for sure.
Here’s a screenshot that may show the bonus reward in action:
M0re details on this interesting theory here.