The best source for really good deals is buying from individuals. Keep your eyes and ears open. Check the newspaper and Craigslist often. Let it be known around town that you purchase coins. A good deal won't hang around for long, so be prepared to act quickly. Don't forget about yard sales. If you see a listing for a yard sale that mentions having coins for sale, try to be the first one there when they open for business on that first morning (even better, be 15-30 minutes early). As I said, a good deal won't hang around long. When dealing with individuals, it has been my experience that it is better to let them set the initial price. Why offer 15x-20x face value when 10x (or less) might be sufficient? Don't "bid against yourself."
eBay is tough. While it is true that with enough patience you will occasionally get a decent deal, its pretty rare...at least in my experience. Look for coins that are improperly identified, listed in the wrong category, or just described badly. While browsing on eBay awhile back I came upon a listing for "5 1909 wheat pennies." After glancing at the photos, I realized they were all VDB's in VG+, but that wasn't indicated anywhere in the title or description. I ended up winning the auction for less than $6 including shipping. Not a monster score by any stretch of the imagination, but one I'll gladly take anytime.
Auctions/estate sales can be a good source as well, especially ones that do not specialize in collectibles. Occasionally you can score at a pawn shop if the owner isn't that knowledgeable of coin values and/or does not keep up with the current price of silver. Sometimes you'll find a bin that has several of a certain type of coin for a set price each. For example, a bin of wheat pennies for 25 cents each or something like that. While that is overpriced for common date wheaties, it is worth the time to go through them looking for key/semi-key dates. I have made a few decent scores this way.
Hope this helps. Good luck!
