Reproducibility refers to the ability of researchers to obtain similar results from replicates of an experiment. If you or others have difficulty reproducing your results, then it will be a real challenge to reach statistical significance. Thus, reproducibility is a key to your ability to draw meaningful conclusion from your data.
To reduce variability, it is good practice to start each experiment with a high-quality sample, limit the length of the protocol to reduce the time that the sample is out, limit the number of steps in the protocol to increase efficiency and reduce the chance of making mistakes, and decrease the requirement for manual manipulation of your sample.