Isn't it obvious, side decking is all about taking out cards from your deck that you won't need and place in cards that you need for your current match ups, hence side decking.
From my experience, I find that they are 2 types of side decking. While they are maybe just player preference, I find this quite interesting.
Type A :
You take cards from your side deck that you KNOW you NEED in the current match and side it into your deck while removing cards that you can do without.
Type B :
You take out cards from your deck that you know you WON'T be needing and exchange them for cards that you MIGHT need in you current match.
You : " Sounds the same ? Isn't the result the same ? And most important of all ... what are you trying to tell us ? "
The end results may or may not be the same depending on styles. Lets take a look at an example.
Lets say your playing X-sabers (I'm familiar with the deck so I'll just use it so that I don't do some mistakes) and your opponent is playing Infernity.
Obvious sides are Shadow Imprisoning Mirror, maybe Saber Hole//Solemn Warning, Compulsory Evacuation Device and Maybe even DD Crow//Effect Veiler//Consecrated Light.
Lets say :
2x Shadow Imprisoning Mirror
2x Saber Hole//Solemn Warning
2x Compulsory Evacuation Device
2x DD Crow// Effect Veiler//Consecrated Light
8 cards ... thats a lot ... but against Infernity, we need extra precautions.
For type A :
You be ... deciding on these 8 cards and then look at your deck for cards that you might not need. Cards like Mirror Force, 1 Emmersblade, Morphing Jar (I use my deck as an example, and this card is in it, so ... ), Dimension Prison and Trap Dustshoot. These are the ones that will go ... but what else ? You might take out a Faultroll or 2 and that Regigura cause the chances of you not playing your loop is higher. The 3rd Gottom's Emergency Call may also be remove since there is Trishula at your opponent's disposal.
You may end up losing a combo or 2 in order to not get kill. Losing your edge but guarantee that you are in a safer position assuming that your opponent doesn't figure out what you sided in.
For type B :
You'll first take out those 5 cards that is universally known as useless. And look more deeper into your deck 1st. You might wanna keep your Faultrolls cause you feel like it. But take out 1 Fullhelmknight and maybe the Rykos in the deck. The 8 cards is sided in.
Ended up with your main combo still in place but the chances of hitting it is lowered.
Basically the same ? And why are you so sure what type A and B would take out ?
Type A players tend to look for defense first. This is shown in the way they take out their side the second duel 1 ended. They wanna survive the next 2 rounds. And think of what they can do to gain more defense as defensive players would do such.
Type B are more offensive. They look at their deck first and look at what they can do WITHOUT and still able to pull off their moves. THEN, they look at their defense.
While these are estimation after looking at duels for so long, they may or may not be accurate//true.
So, take a look at your opponent after duel 1, is he looking through his deck 1st or his side. Then you could have a rough idea how aggressive a player your opponent is. And try to think like him and guess the sided outs and ins.
BUT, if your opponent is World Championship level players or Regional winners ... They know their deck inside out and most probably yours too ... so, they will side in the cards they KNOW will work and those that they KNOW won't work. So don't depend too much on what I wrote if your opponent is a top notch duelist.
YOU : "So, your saying that what you just wrote is useless if I'm a pro ... "
Me : "If your a PRO ... why the hell you need advice from me?"