John's dashboard

Your best bet is to use http://search.twitter.com. Twitter Search looks through the content of all tweets posted in the past few months for the string that you enter.

Using Twitter to post a one-off classified ad probably won't do you any good. It takes a lot of time to build up your Twitter followers, and signing up to post a tweet that barely anyone sees initially won't work well for you.

There's two answers to this question - depending on what you are trying to do. I'll take you through each one.

If you are trying to keep Twitter on your profile, but you don't want it to update your status, do this:

1) Login to Facebook
2) Put your mouse over the "Settings" menu item in the upper right-hand corner of the page, located in the blue header on every Facebook page.
3) When the pull-down menu appears, click "Application Settings".
4) When the next page loads, you will see a list of your applications. Locate Twitter. To the right, you will see a link that says "Edit Settings". Click it.
5) A pop will appear, giving you several options. One of the main navigation menu items is "Additional Permissions". Click it.
6) You should see a checkbox that says "Update my status without notifying me" next to it. Uncheck it.
7) Click "Okay".

You are done. Twitter will not update your status any longer.

If you would like to remove the Twitter application altogether, do this:

1) Login to Facebook
2) Put your mouse over the "Settings" menu item in the upper right-hand corner of the page, located in the blue header on every Facebook page.
3) When the pull-down menu appears, click "Application Settings".
4) When the next page loads, you will see a list of your applications. Locate Twitter. To the right, you will see three columns, one with a blue "x" in it. Click it.
5) A pop-up will appear, asking if you want to remove Twitter. Click "Remove."

Bam. It's gone!

Adding this feature would add a lot of complication to Twitter. How will users determine who can / cannot see those posts? Would there have to be another button somewhere on the UI to say "Allow this person to see my private tweets"? I think managing this could be too complicated. Twitter needs to focus on a revenue producing business plan, not additional features. It seems like with over 750% growth last year, most people are satisfied with the current feature set.

You can also setup private groups using Twitter on http://www.tweetworks.com/, and chose whether or not to post to only the group or to the Twitter public timeline.

Let's not forget about direct messages.

Depends why you want to do this -

Twitter is different than other social networking sites in that - well - it's up to you to build your network, rather than choosing, say, a geographical area or organization to join like on Facebook.

One way to find people is to use their search tool on http://www.twitter.com. If you're looking for dog owners, for instance, you might search for "pets" or "dogs". This tool will search throughout profiles on Twitter for the string that you enter in the search box.

Another way to find people is to look at some of the people your friends are following - or even at the people that are following them. You might find some people with similar interests.

Lately I've been coming across several blog posts, listing out people in certain professions. You may want to search google for "My Profession On Twitter", replacing, of course, "My Profession" with whatever it is you are looking for - for instance, "Doctors on Twitter, "Dog Owners on Twitter", or "Book lovers on Twitter".

Lastly, you can use http://search.twitter.com to find people tweeting about certain things. While the people search found on the Twitter website only looks at profiles, http://search.twitter.com will look for whatever term you use inside of the content of the tweets themselves.

Hope this helps.