Zeb's Quick Guide to Interacting in Google Plus:
1) you can 'follow' people without them approving, you only see their public stuff.
2) people can 'follow' you without your approval. they only see your public stuff. (yeah, I know, but I've seen so many questions about this)
3) for anyone to see anything more than your public posts, they have to be in one of your circles and you must post the content to that circle(s)
4) 'Incoming' is for people who follow you, but you don't follow them (this only shows up here, not in your main 'stream'. Once you get some people in this area, this is a great place to find new people to connect with.
5) 'Following' is for people you want to follow but don't expect a follow back and don't fit in a different circle i.e. celebs, bloggers, etc.
6) when you post you chose who you want to see it. adding public allows anyone to see it. if you just use "extended circles" then anyone in your circle(s) and anyone in their circles can see it. of course you can limit to one or more circles or one or more people or any combination there off.
7) Consider creating a 'bulk follow' or some similar named circle when you're starting out and follow a bunch of people in this (i.e. people you see mentioned in other posts) use this circle to filter people you add to 'following' or other circles.
8) think twice before adding +Chris Pirillo
or +Robert Scoble
(seriously, add people like this to a "talks alot" circle)...
9) Make Google+ what you want it to be. I use it for interacting with a large amount of people much like I use twitter. But that doesn't keep me from having close friends and family circles and have the interaction that used to be on FB. I'm also starting to build some of the similar circles I have on flickr. You can make your circles exactly like you want them and after using it for a day or two you'll make some changes and soon you'll be sharing and seeing exactly what you want to with exactly the people you want to interact.
10) have fun and good luck.