Then, decide what you want to learn about. Pick two to ten things that interest you: knitting, NASCAR, rabbit raising, fishing, NBA, etc. For each of these, if you already were to know a famous person in that category, say Dale Earnhardt, Jr., or Danica Patrick for NASCAR, go find out his or her Twitter feed. Type in the name in search box under "Who to Follow" link on Twitter. Just be warned that some celebrities have had pranksters (or earnest fans) create fake accounts in their name: some of these accounts are useful, some are not. Click on their name, then "View Full Profile." "Follow" him or her. Then go to that person's "Following" list and Follow the whole list-- everyone on the list. Don't worry for now as to getting "too many"-- you'll weed out the creft later. On to your next interest. Say you're a huge fan of Pixar movies and like especially the ones directed by Andrew Stanton. Find him-- his userid is actually "6Mman", and follow everyone he's following. You could also just search for a topic -- try "rabbit raising." Follow everyone.
Perhaps you need some more. Go to wefollow.com, and search for some celebrities your admire or topics you are interested in. For example, if you're a Lutheran, you could go search for "lutheran" . Follow lots and lots of people-- maybe both Nancy Pelosi and John Boehner. Again, when you find interesting persons, go and follow ten or twenty people that they follow as well.
Hopefully, you will have gotten to a thousand people to follow. One mistake I made when I started Twitter was worrying too much about all the textual garbage that shows up when you view the tweets a person has made when you "View Full Profile". There may be many messages to individual Tweeps in the form of "@Johnny blah blah blah" but these won't show up in your view of Twitter unless you also follow the person addressed. Use instead the quality of tweets in your timeline to decide whom to unfollow.
Now weed out the creft.
Now look at your Timeline. Some people on twitter are saying or sharing links to things which are witty, entertaining, inspirational, or highly useful all day long. On the other hand, some people are repeating themselves every few hours, engaged in inside jokes, puffing themselves up, making a half-dozen posts in a row, and other behaviors that wouldn't be tolerated at a dinner party. Unfollow them. You don't have to apologize, this is not a social friendship in the same way that Facebook friends are. Think of them as news feeds. Do you apologize to CNN for turning off the channel? There are also a number of practices that some Tweeps engage in that are not helpful. If you see someone you admire say something like, "Follow my friend @Johnny, he has links to great steak recipes," that is, give a reason for following him, you may want to follow Johnny. If however you see, "#FF @Johnnie @Billie @Suzie @Millie @Maureen @Doreen @Squidleen", then you probably want to unfollow this person. There is a silly tradition by some to just blindly mention names of people to follow. If you watch these tweeps, you'll find that some of them recommend the same folks over and over-- get out while you can. I find it annoying. There's also an absurd tradition to "Retweet" the "#FF" when you get mentioned; probably some fools who will offer thanks back for the retweeted #FF. Do you see the point? At a dinner party, a friend tells you "Johnny thanked me for thanking him." ???!! It pollutes the stream with text that our already overloaded eyes have to jump over to get to the next tweet. Another pet peeve is multilingual tweets. I'm unfortunately monolingual, so if someone posts even 10% of the time in another language, my eyes get tripped up as it takes me a few seconds to figure out it's a different language.
What's the optimal number of people to follow? Well, for basic users, Twitter has a limit of 2000. My advice first is to grab quickly a thousand people who might seem to be interesting, then weed out any and everyone over the course of a few weeks who makes a single post that is either annoying, uninspiring, or unintelligible to you. You'll probably still have a few hundred, and just check the stream when you can.
If anyone else is boring, tweets too much, or gives unintelligible information, get rid of them. This is your feed. Don't worry about having more total tweets coming in to your timeline than you can read in one day. Twitter is like a dinner party, or a webcam feed from the coolest dinner party ever. Tune in when you can, then turn it off and get on with your real life.