Most successful trading uses technical analysis of the price chart to determine both entry and stop-loss price levels.
There are many freely available strategies which you can research and use in a demo account until you find one that suits you and which you can make work profitably. Any decent strategy will link both entry and stop-loss levels. Until you have a strategy which is consistently profitable in demo, do not attempt to trade with real money.
A stop-loss order is an order placed with a broker to buy or sell a specific stock once the stock reaches a certain price. A stop-loss is designed to limit an investor's loss on a security position. For example, setting a stop-loss order for 10% below the price at which you bought the stock will limit your loss to 10%.
Before setting a stop loss, you should try to determine the market movement. A static stop loss at 30-35 pips doesn’t always work. If a market is volatile, you need to place a wide stop loss, whereas in the quiet market a narrow stop loss can work.
I also think entry points are crucial. Learn more about technical analysis and choose a strategy - trading based on support and resistance is a good one, for example, not too difficult to get the hang of it, relatively speaking. You could also look into trailing stop losses.