1) Wait till Dark.
Too many fisherman fish just before dark and as you can catch fish like this especially school fish this encourages this behaviour. I strongly advise against this and haven’t seen anyone to date pull a fish bigger than 4lb before Dark. In fact, the pool they fish will seem quite dead as they fish the pool through. Often, I will fish the pool after it has had some rest and the same pool will produce fish and often big fish. It is not a coincidence that those fishing early rarely hit anything big and rarely catch fish plural. I like to wait until its Dark! Often, I will wait until its dark and then wait 15 minutes just to be sure. Doing this has certainly helped aid me in catching many sea trout. Although hard to do especially in the summer months were it's light until 23:00 this is a great tool to add to your armoury and one I strongly advise.
2) Fish Short Leaders.
Another quick fix is ensuring that your leaders are not too long. The key reason behind this is that you need to be in contact with your fly as it fishes a swim. Any long-time sea trout fisherman knows that a take from these wonderful creatures can be as gentle as a butterfly’s kiss and any slack in the line and you’ll miss it. Also, if fishing a sink tip or sinking line a shorter leader will ensure that the fly gets to the level you wish it to be fishing at a lot faster. This can be very important as fishing the correct depth is a crucial factor in sea trout catches when fly fishing. I recommend a leader of 10-12lbs Fluro or Mono, with a length 6-9ft Maximum ( 6ft for single flies and 9ft when fishing 2 flies ).
3) Fish close to the opposite bank.
One of the best sayings when it comes to sea trout fishing at night is, ‘If you are not losing flies, you are not fishing close enough to the opposite bank’. This is good advice as 99% of my fish caught are from casts that have, even if not producing straight away, started tight to the far bank. Sometimes people will get takes in the middle of the river and a lot of the time this creates misconceptions as often the fish has followed it from tight against the bank and taken it as it's swinging around in the current. I am not saying you won’t catch fish in the middle and in the tail of pools this is often a good area to cover, but you will catch more fish casting tight to the far bank.
4) Fish big Flies
People are obsessed with small flies. It seems as consumers we are brain washed into the theory big fish only take small flies. So much so that most modern-day hooks now label larger hooks at smaller sizes just to make the customer happier in purchasing these hooks. This is as far as I am concerned garbage. They will take small flies, they will also take large flies and in fact when fishing for sea trout as they are not eating, the larger flies are a better bet. They imitate small fish and can provoke aggressive responses from territorial predatory fish. My own innovation of the stinger series which see some very well-known patterns modified to be larger and include a flying inverted single have been a breakthrough in modern-day sea trout fly fishing at night. Incredibly light and easy to cast they are large and create a great profile which is what you want from any sewin pattern. This is the only fly me and my farther-in-law have fished with in which 100% of sea trout hooked are also landed. You will still get tugs and pulls as with all sea trout fishing however once they are on, they are on! The single used is incredibly strong and has no problem in playing a double figure sea trout.