From LOTR-TCG Wiki

Filtering (or thinning) is an informal game term. It means to remove useless or situationally-irrelevant cards from your deck, generally by searching your deck for them. You've "filtered" out cards, meaning that you have a "thinner" deck composed only of the cards you actually want to draw. Typically, players will want to filter Free Peoples cards out of their decks as quickly as possible, to have hands full of Shadow cards for the important late-game turns.

One of the strongest filter strategies in the game "Horn filter", a strategy from Expanded using Erkenbrand's Horn (18R96) . You pack your deck full of Followers, then use the Horn over and over to put them all into play. This is especially powerful in conjunction with Gamling, Defender of the Hornburg (11R147) to download it on the first turn, and New Chapter (13U154) , to heal the exertions from using the Horn.

Game Setup Starting FellowshipBiddingMulligan
Deck Building Considerations UniquenessX-ListR-ListErrataFormat
General Strategies BeatdownBombCorruptionHand ExtensionRun/StopSkirmish CancellationSwarmWin ConditionWound PreventionWounding
Deck Archetypes Auto-Corruption BombBeasterlingsBerserkersBouncing HobbitsElventsForestgulsHobbit HospitalFruit LoopsGondor KnightsGondor RangersGondor WraithsMoria ArcheryMoria BeatdownMoria NavyMoria SwarmMoria TentaclesNazgul BeatdownNinja GollumOrc CorruptionRainbow WoundingSauron GrindSauron InitiativeSauron RoamingSauron ThreatsSolo SmeagolSouthron ArcherySouthron InitiativeStupid SwarmSuper FriendsTelepathyThreatgulsToken TanksTroll SwarmUruk ArcheryUruk MachinesUruk TrackersWarg Super Swarm
Rules Rule of 4Rule of 9
Mechanics BearDiscardDraw DeckExertExhaustedFellowshipInitiativeIn Play/Leave PlayMove LimitReconcileRoamingSite ControlSpotStackSupport AreaThreats
Gameplay Terms BoatBodyBroken/NPE/OPBuff/NerfChokeComboCultural EnforcementCyclingDead DrawFetchFilterFloodGrindHand ClogHateInteractionItemLoopMatchupMetaMillNewbie TrapPilePower CreepPumpRainbowRecursionRemovalResourceRogueRule of 6SideSite ManipulationSpeed BumpSplashSubcultureTankOther Terms