Use this card when your opponent controls Tokens and/or Fusion/Synchro/Xyz Monsters. Your opponent will be unable to Summon monsters from this card's effect, since their monsters weren't shuffled into the Main Deck.
If your opponent targets a "U.A." monster(s) you control for an attack or a card effect, activate this card to interrupt their play.
Similarly, if your opponent activates a card effect that would negate the activated effect of a "U.A." monster(s) you control, Chain this card so that your effect won't be negated (as your monster will no longer be on the field when your opponent's card effect resolves). This works for most cards, barring things like "Abyss-scale of the Kraken" and "Memory Loss".
Chain the effect of "U.A. Midfielder" to this card's activation, giving you greater control over which "U.A." monsters you shuffle into the Deck.
Keep in mind that since you shuffle at least 2 of your "U.A." monsters with different names into the Deck by this card's effect (unless your opponent Chains a card effect that only leaves you with 1), you can Special Summon those same monsters from the Main Deck, since this card's effect doesn't require the Special Summoned "U.A." monsters to have different names from the ones you shuffled in, only different names from each other.
Combo this card with effects that Special Summon your Main Deck monsters to your opponent's side of the field, such as "Flying "C"", "Santa Claws", "Lava Golem", etc. Since those monsters will be shuffled into your Main Deck, you will be able to Special Summon additional "U.A." monsters from your Deck.
Key monsters for you to Special Summon with this card include:
"U.A. Rival Rebounder" during your opponent's turn, so that you use that monster's effect to Special Summon an additional "U.A." monster from your Graveyard.
"U.A. Blockbacker", especially if this card shuffled a card(s) into your opponent's Main Deck. If your opponent chooses to Special Summon a monster(s) by this card's effect, you can use the effect of "Blockbacker" to negate their effects.
"U.A. Midfielder" during your Battle Phase, allowing you to get an additional attack in by using that monster's effect.
If you control "U.A. Stadium", use this card during your opponent's turn so that your Special Summoned monsters will gain 500 ATK.