Buying and Selling

Looking at the trend and finding out if it is upwards or downwards for GBP/USD and EUR/USD, how about buying or selling in one pair  because it looks to me its slow moving and wait for 10 to 20 points taking a 2nd position in GBP/USD according to trend.If one position in EUR/USD is going in negative the other one in GBP/USD should be in positive. GBP and EUR do go in cross but for short period and I have noticed they are moving together most of the time. So trading in currency is always in your benifit but you must put your eyes on it. So which may cause increase your profit.