It is always good to write down the stop loss price before you enter the trade. Initially a fixed stop loss and then if you are good with direction you can move to trailing stop loss. You can move your stop loss up as much amount the underlying price is up
To define initial stop loss you can follow the below calculation, first define your risk of loss between 0.5 to 2 percentage of your trading total. For example if you have 100000 rs as capital, you should risk only 0.5 to 2 percentage of capital. Say for example if you opt 2% then the risk amount should be 2000 Rs So if you are buying 100 shares at 20 Rs rate, the total is 20000 the amount you can risk is 2000 Rs, so set the stop loss at 18 Rs per share. So when stock moves up you can set 2 rupees below as trailing stop loss.
Hope this helps
Most people prefer SL-M to ensure that they don't end in bad numbers as all the quantity will be sold out immediately.
But I understand if volumes are huge say 2000 above, one would like to use SL-L.
One risk factor associated with SL-L is that your order may become partially complete with some quantity pending (if you set Limit Price too close to trigger price).
This is my suggestion, (Assume you set a stop loss sell order) first decide the Stop Loss Limit Price below which you don't want your trade to end up with. Then take around 0.3% of the stock price and set the trigger above it.
Example:
Your buy price is 300, Target is 310
You decide Stop Loss Limit Price as 296, so trigger is approx 300 x 0.3 /100 = 0.9 points above 296
So you need to create a stop loss - limit order with Price as 296 and Trigger as 296.9
When price hits 296.9 (trigger) your order will be placed as limit order 296, since market price is already higher than 296, your order will tend to execute at best available market prices, until it will reach 296. Most probably all your shares would get executed in this range for highly liquid stocks).
If some quantity is pending, (most probably it wont), you can wait until price comes back to 296 or you could cancel the order and sell those stocks at later part of the day (since risk associated with only small number of unsold shares is less comparatively, you could wait and see if price regains).