Craigslist is a great place to get a good deal on both new and used goods. Ads on craigslist only last a week and inventory turnover is very fast in many locations. If you are looking for something popular, it's likely that one or more sellers already has one for sale on craigslist today. For rare items, you need to have a bit more crafty. The hard way is to remember to search for the item every day on craigslist. This works, but requires a lot of effort and remembering. If you make it part of your daily routine such as doing it right after you wake up, this can help. If you use feed reading software, you can also set up an RSS feed for any craigslist for sale search which alerts you when something becomes available. This is a good idea if you already use a feed reader to follow blogs and news sites.
Another easy approach is to set up a Google Alert for a certain keyword. Google will alert you by email when a certain keyword shows up on your local craigslist site. Keep in mind that it may take a few hours or days for Google to contact you so someone else may have found your item on craigslist first and purchased it. With some patience and strategy, a savvy buyers can get great deals on craigslist and be one of the first to see affordable items of various types for sale on the site. Most items will resurface and be posted by someone else, so do not feel the need to buy the first one you see without it's an incredibly good deal or if amazingly rare.