could you be a little bit more specific? What exactly would you like to sample? Makro, micro or nano plankton? In your case I would check the literature and see what other researchers did for specific sampling types.
For example, here is an article comparing two different types of plankton sampling nets.
If you can access to it I can highly recommend this book which explains in great detail all variations of plankton sampling in Chapter 4 "Sampling methods for plankton":
Greetings sir Hannes Reinwald , Thank you for reaching out, I am trying to find out a scientific method for zooplankton sampling. Sorry, I did not mention the types or size of desired planktons earlier because I am not conducting any research yet for plankton sampling. As I am a first year student, I am expecting to learn a theoretical explanation generally on what is actually a kitahara/hensen/wiconsin net, and how to conducting a sampling using kitahara net properly as well as preservation method. For now, I cannot access to the journal and article you share earlier but really Thank you. :)
Dear Muhammad, good luck for your studies. If you liked my answer and find it useful feel free to click the "Recommend" button so others will find useful answers quicker.