Jesse Newhart has put together a good, 8 minute overview of how he effectively follows a high number (15,000+) of people on Twitter using Tweetdeck. I use many of the same strategies for following a lesser number on Twitter (2000+), and if you do follow a significant number of people, these ‘tricks’ are useful if not essential.
And while I am writing this, I just noticed that Brian Crosby has asked “why would you want to follow 15,000 people?”. I think the video may itself help to answer this important question as Newhart does explain each strategy in context (e.g., looking for links, helping to answer people’s questions, noticing popular trends among followers). While I do not follow that many, I know that I do benefit from following more people than I can regularly engage.