Leverage simply allows traders to control larger positions with a smaller amount of actual trading funds. In the case of 50:1 leverage (or 2% margin required), for example, $1 in a trading account can control a position worth $50. As a result, leveraged trading can be a "double-edged sword" in that both potential profits as well as potential losses are magnified according to the degree of leverage used.
It is hard to determine the best level one should use, as it mainly depends on the trader's strategy and the actual vision of upcoming market moves. As a rule of thumb, the longer you expect to keep your position open, the smaller the leverage should be. This would be logical, as long positions are usually opened when large market moves are expected. However, when you are looking for a long lasting position, you will want to avoid being 'Stopped Out' due to market fluctuations.
In forex, investors use leverage to profit from the fluctuations in exchange rates between two different countries. The leverage that is achievable in the forex market is one of the highest that investors can obtain. Leverage is activated through a loan that is provided to an investor by the broker that is handling the investor’s or trader’s forex account.