This is a popular method used by many professional traders and is actually quite simple to master.
It basically involves entering a trade and then taking the majority of your profit as soon as you hit a pre determined target and then leaving the last remaining lots to run for a much larger profit whilst eliminating your risk with a stop at break even.
For example you may decide to take your main profit as soon as your 30 pips into profit or you may have identified another level of support or resistance that you will use as a primary profit target.
After taking your initial profit you can then set more profit targets deeper into the trade and look for some large move on your remaining lots.
There is no set way to do this as there are many options so it all depends on what you feel most comfortable doing.
The benefit of this method is that you are usually taking small profits more often which makes you feel like you are taking more winning trades which can be a boost to your psychology and help you to keep trading consistently.
The negative aspect of this strategy is that if you have a few losers they can seem to dwarf your winners especially if you have only been taking your initial target on your last few winning trades.
This can cause you to become dismayed with your trading and feel as though you are making no progress.
The reality is that over time as you collect more and more nice runs in price these moves will outweigh the losing trades that you have.