Username: You can pull in a public user's public posts by connecting their profile URL. You'll see accounts with formats like https://plus.google.com/106766146657870989685 or https://plus.google.com/+RyanMacInnes, you'd enter
Google Places: You can also pull in the reviews of a location from Google Places. Use this tool to find out what the place_id is for the location, then enter that as a new GooglePlus Username source in Juicer and append a * before it, something like:
*ChIJj61dQgK6j4AR4GeTYWZsKWw Google will only allow you to pull in a few reviews at a time, but they should build up over time if you let it go for a while.
Hashtag: Simply enter the Google hashtag you want to pull in after clicking the GooglePlus logo, then clicking the "hashtag" tab at the top of the overlay. Juicer will pull in any public posts it can for this source.