How to choose the right "Side Deck" cards?

Hey RespectYGOers! Happy new year to ya'll! It's me, Arcknight , and I'm back with a new article. This time, we will talk about a strategy that some may overlook: Side Deck. A lot of meta decks right now either focus on 1-card combos, spam a lot of negation or have floodgate to control the game. Your side deck does a lot of job in countering these strategies especially if it will affect your gameplay. Now, what are the things that you need to consider in choosing the right side deck?