Twitter strategies?

Has anyone had any success using Twitter to increase sales or engage customers? If so, can you recommend any strategies that seem to work?

Thanks
Mikey

What advice I have heard is to keep at least 90% of your tweets ad free and human interest type of things. This keeps you in the mind of fellow twits. I have had a number of customers say they saw my tweet about something in the neighborhood and decided today would be a pizza day.

Thanks Daddio. Along those lines, I think the challenge is finding something relevant that is somehow connected but not ‘spammy’ among so many choices. It seems chaotic and I think for some Twitter has been great, but for others not at all, and I am trying to gage the effort needed to make it worthwhile.
On the one hand it seems to easy to just tweet. On the other- I think more thought is needed than a quick tweet on, say, a cool article you come across, to have it succeed. perhaps I am over thinking it?