bumblebee, first you need a strategy or plan or set ouf rules what the trigger should do. It helped me for my first trigger file to note down what I did and why I did that while betting via betfair website.
Then I tryed to translate the written notes into a trigger file. Run the trigger in test mode first until you are perfektly sure that the trigger is working as expected.
Next step: make the trigger secure. Add conditions to forbid any actions in case the market is not as expected. i.e. bad Book %, low liquitidy, to fast or to slow moves, or wrong markets (maybe a soccer trigger works well for tennis, too.)
Run the trigger again in test mode and if the trigger still works and has passed some "strange markets" tests, try in real mode with a most of your bank hidden in Australian wallet.
Trigger are designed for unattended use, but i would strongly suggest you to watch triggered operation for some days.
Never forget to check if triggers are still working if you do a minor change with the trigger file.
Never run your trigger in InPlay markets first, in case of an error usually there is no change for a stop loss with small loss ad odds move very fast doring Inplay.
You can use triggers from trigger library too, all I used from trigger library worked fine for me, but I added some security conditions to avoid trading when market is not suitable for my triggers.