Ideally there is a complete theory on this you have to enter on primarily when there is either a breakout, reversal or continuation of any major pattern, in this you take confluence with some indicator that you have in your arsenal and then prepare some pivot points for take profit and stop losses. This way you trade appropriately finding the correct points of trading.
But this does not still mean trading is easy, the theoretical part can be easy but to make profit often may not be easy. You are right that using stop loss is very important, I started to use Bollinger Band and Relative Strength Index and I make some profit, but my take profit is not that of a long range and I am cool with just the little profit I make. Some traders do not make use of trading indicators but just trade like they are gambling which makes them more vulnerable to losses.