Currency strength can be used to trade a wide range of market conditions, including trend, counter trend and range, but the easiest for the majority of trading strategies to trade will be with the trend. When trading trending markets you should buy a strong currency (>+3) against a weak currency (<-3). Good examples to look at for this will be pairs listed under possible trending buys or sells on the list above.

When you've identified a strong/weak pair, you then need to identify where price is within that trend before entering. Ideally, at the time of entering a trade, you want price to be within either of the green zones illustrated in the uptrend example below. This will mean you are trading in the direction of the trend, and have enough room left in that move to reach a profit target.  

If you wish to trade counter trend, you should look to sell strong currencies against weak currencies, expecting their roles to reverse, with the strong becoming weak and the weak stronger. Good examples to look at for this will be pairs listed under possible counter trend buys or sells on the list above. Again, you should also study their respective charts very closely before entering any trade and you ideally want pirce to be entering either of the red zones illustrated on the example below. These zones are where the trend has become exhausted and a counter trend move is more likely.