Track Record

There is no "holy grail" in trading, not in any market; in other words, there is no such thing as a trading system or strategy that wins 100% of the time. However, before you start trading someone else's system, you do want to have some idea of how successful they have been in the past. As all those investment fund ads say, past performance is no guarantee of future success, but at the same time if someone is trying to sell you signals and they have been losing money every month since they set up in business, you will probably want to avoid them! All services will have some sort of track record published on their website, and the more detailed the better. You at least want to be able to see a breakdown of profit by currency pair, as their total figures are likely to include more pairs than you are going to be trading in one go.
http://www.forexheaven.com/forex-advisory-services.html