You mention "Tweet a link to something funny or informational that someone else created" - Is there a way you prevent from posting duplicate or similar items with the rest of the stream? I find that a lot of the twitter feed is the "most popular" items of the day or the most recent RSS updates (from HN, SAI, etc.), especially when the follower base is so focused.
I just make sure that I hand curate any links that I post. So I never "automate" the selection of links, that is an entirely manual process. In that way I can be sure that I only ever post stuff that I really like and that I never double post anything.
If you mean how do I stop tweeting the same thing that someone else tweeted... I wouldn't know how to go about doing that...
