To expand on Sarah's answer, think of Twitter as a big networking event. Overhear a problem, gracefully nose into the conversation if you have a solution. If the challenge is something related to your product, such as the prospect tweeting "I am so sick of using SalesForce for my CRM!", you could reply with "@person, Overheard your SalesForce comment - I used it myself in the past. What do you wish SalesForce had or did differently?" If you want to get into advanced techniques to identify these trigger events and respond to them in a way that gets people into a purchase, let me know. If you're going after prospects who have not expressed a frustration with their current solution or a desire for a product like yours, then Twitter is the wrong platform for outreach, and we could come up with a strategy for leveraging a different place to get better results.