If you were able to change one thing about a experiment that has gone wrong or failed, what would it be, why and what

Question: If you were able to change one thing about a experiment that has gone wrong or failed, what would it be, why and what happened?
- Keywords:
  experiment,
  method
Asked by NobeliumHoliumMolybdenum to Sudhin, Sergio, Katie, Frances, Diarmuid, Aoife on 14 Nov 2019.
- Sudhin Thampi answered on 14 Nov 2019:
  
  it is never one thing or one time but it takes many attempts and modifications to make it work!
- Katie Fala answered on 21 Nov 2019:
  
  Often I try to solve it by myself, but doing a PhD and science in general takes a village (thanks E!). I often notice that I would have resolved things sooner if I had gone to ask colleagues for help sooner instead of being stubborn.

Question: If you were able to change one thing about a experiment that has gone wrong or failed, what would it be, why and what happened?