The best time to start investing in silver is usually in (latish) October. When silver starts moving, and plays catch up with the gold price. However I have noticed that silver, and gold prices are running petty much in tandem, so I see little advantage in holding silver over gold at this moment in time. There is nothing wrong in holding silver right now. Just be really cautious around about the end of February when silver can start to falter.
A little out of date but you may or may not find this interesting:
http://www.yukonzinc.com/documents/SilverLeverage-Jensen2005-09-12.pdfYou may also want to look here:
http://silverstrategies.com/PerformanceReport.aspxAlso the excellent site that Davidslane brought to our attention:
http://www.resourcestockguide.com/home_page.phpOne problem with silver is that you never really know whether the market is valuing it as a precious, or an industrial metal.
Good Luck.