1. Using Position Size Instead Of Technical Analysis To Determine Stoploss
Don't let your lot size determine your SL value. It should be the other way around. If you pick your entry using technical analysis, then you should do the same for your Stop loss.
2. Placing Stop loss Exactly On Support Or Resistance Levels
3. Placing Stop loss Depending On the Market Moves
4. Placing Very Tight Stop loss On Trades
If the stop loss is too far away, this may reduce your risk to reward ratio. If your stop loss is so close to entry, you will be stopped out easily.
5. Placing Stop loss Too Wide.
Always place stops where analysis is invalid.