“Love the Lord with all your heart, and with all your soul,
and with all your MIND”--Matt 22:37
“Every Christian is a missionary to the extent that he or she has encountered the love of God in Christ Jesus” --Pope Francis (Evangelii Gaudium, #120)
Question: Do the Jehovah's Witnesses (JWs) get some things right?
Answer: sure. 
But they certainly get a lot of things wrong.
(Caveat: I am not an expert on JW beliefs, so I would recommend everyone use as healthy a dose of skepticism as we would if a JW wrote about what Catholics believe. However, I also don't think I'm wrong about what I'm presenting as JW beliefs. 
)
)
As far as what the JWs get right--we can appreciate their love and knowledge of Scripture, their zeal for God (whom they call Jehovah), and who can look down on their great courage in going door to door, trying to evangelize. They certainly put us Catholics to shame in knowing how to be "witnesses" for the Word of God. Would that Catholics were better missionaries--with the Truth of the gospel with us, we could conquer the world!
However, sadly, we Catholics are notoriously easy targets for the JWs--in fact, a large percentage of JWs were baptized Catholics--because we have been poorly catechized. It seems that in their door to door evangelization, the JWs find many a Catholic who has never learned the Truth of the Gospel, and thus falls for the false teachings of the JWs.
If we are knowledgeable about the Faith, we should invite the JWs in and ask them about their journey. More likely than not, they will have been baptized in the Catholic Church, and we can ask them what they knew about the Faith they left. (Most likely answer: not much, although most JWs are loathe to admit that and will instead say, "I was an altar boy! I went to Mass in Latin every day!" But if you ask them a very simple question such as, "Where in the Mass is Scripture?" they won't know the answer. (Answer: Scripture is in the Mass everywhere!*). Another very simple question they often can't answer is "What is the Immaculate Conception?" More likely than not they will refer to the virgin birth, that is, Jesus being conceived in Mary without sexual relations. However, that is NOT the Immaculate Conception. The IC refers to Mary's conception in her mother, St. Anne, and being free from Original Sin from the first moment of her existence.)
In my discussions with JWs I often hear a lot of "Catholic canards" such as, "Catholics believe that Mary can get you into heaven through the back door, without Jesus even knowing!" and"Catholics believe that all non-Catholics are going to hell". They are adamantine that since Sr. Mary McGillicuddy told them this, that this is the gospel according to the Catholic Church.
Most likely they were either taught wrong, remembered wrong, or simply misinterpreted what Sr. Mary McGillicuddy told them. At any rate, any time an ex-Catholics proclaims that she was taught something that doesn't sound quite right, the best thing is to ask them to provide a source. (Note: for it to be a Catholic teaching the source has to be a document from the magisterium, not from a random Catholic, or priest or even a bishop or pope who is not speaking in his official office).
It is sadly true that the Church in the past did an abysmal job providing nourishing catechesis for her flock. So it's no wonder that as Catholic folks grew up and started searching for truth, they went where they thought they were being fed. But if they really knew what their Mama taught, they wouldn't have left!
So what is a good way to evangelize a JW who comes to your door?
Start with John 6, which is the Bread of Life discourse--the backbone of our belief in the Real Presence of Christ in the Eucharist.
As far as where the JWs get it wrong, here's a list of some of their beliefs, which are grounded in some rather grave misinterpretations of Scripture:
-Jesus Christ is NOT God, but rather the son of God who is a perfect human being
-Jesus is a reincarnation of Michael the Archangel
-There is no such thing as hell because there is no such thing as an immortal soul
-Blood transfusions are prohibited by God
-Observing holidays (including Christmas) and birthdays are prohibited by God
____________________________________________________________________________
*Where is Scripture in the Mass?
Introductory Rites:
Sign of the Cross:
"In the name of the Father, and of the Son, and of the Holy Spirit." (Matt 28:19; cf. John 14:13-14; Acts 2:21)
Liturgical Greeting:
"The grace of our Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all." (2 Cor 13:14)
"Grace to you and peace from God our Father and the Lord Jesus Christ" (Phil 1:2; Eph 1:2)
"The Lord be with you." (2 Tim 4:22; cf. Matt 1:23; 28:20)
People's Response:
"And with your spirit" (cf. Gal 6:18; 2 Tim 4:22)
Rite of Blessing and Sprinkling Holy Water (see Ezek 36:25; cf. Num 8:7a)
Penitential Act:
Intro: "Let us acknowledge our sins, and so prepare ourselves to celebrate the sacred mysteries." (cf. Ps 51:5)
"I confess to almighty God..." (cf. Lev 5:5; Neh 1:5-9; Dan 9:3-19; James 5:16)
"Have mercy on us, O Lord. / For we have sinned against you. / Show us, O Lord, your mercy. / And grant us your salvation." (Ps 41:4)
"Lord, Have Mercy" (Matt 15:22; 17:15; 20:30-31; cf. Ps 123:3)
Gloria:
"Glory to God in the highest, and on earth peace to people of good will" (Luke 2:14; cf. Rev 4:11; 5:11-14)
"We praise you, we bless you, we adore you, we glorify you..." (Cf. Ps 148:13)
"Lord Jesus Christ, Only Begotten Son" (cf. Ps 2:7; John 1:14)
"Lord God, Lamb of God, Son of the Father, you take away the sins of the world..." (cf.
John 1:29)etc.
Prayers concluded by "Amen" (Neh 8:6; Ps 41:13; Rom 16:27; Heb 13:20-21; Rev 7:16)
Liturgy of the Word:
Introductory/Concluding Dialogues:
"A reading from the book/letter of..."
"The Word of the Lord" (1 Peter 1:25) - "Thanks be to God" (Rom 6:17; 2 Cor 9:15)
"A reading from the holy Gospel according to..." - "Glory to you, O Lord"
"The Gospel of the Lord" (Rom 16:25; Mark 1:1) - "Praise to you, Lord Jesus Christ"
Acclamations before the Gospel:
"Alleluia" (many Psalms, esp. Ps 146-150; Rev 19:1-6)
"Praise to you, Lord Jesus Christ, King of endless glory!" (cf. Ps 24:7-10; 1 Thess 2:12; 2 Tim 4:18)
"Praise and honor to you, Lord Jesus Christ!" (cf. Dan 4:34, 37; 1 Peter 1:7)
"Glory and praise to you, Lord Jesus Christ!" (cf. Phil 1:11)
Profession of Faith:
"I believe..." (Mark 9:24; John 11:27; cf. John 14:1; 1 John 5:10)
General Intercessions:
"We pray to the Lord" (Exod 8:29-30; 10:17-18; Jer 42:2-4; Acts 8:22-24)
"Lord, hear our prayer" (2 Kings 20:2-5; Isa 38:2-5)
Liturgy of the Eucharist:
Preparation of the Gifts:
"Blessed are you, Lord God of all creation..." (cf. 1 Chron 29:10; Ps 72:18-19; 119:10; Luke 1:68)
"Blessed be God forever. " (cf. Gen 14:20; Ps 66:20; 68:35)
Eucharistic Acclamations:
"Holy, Holy, Holy Lord God of hosts..." (Isa 6:3; Rev 4:8)
"Blessed is he who comes in the name of the Lord." (Ps 118:26; Mark 11:9; Matt 21:9; Luke 19:38; John 12:13)
"Hosanna in the highest" (Mark 11:10; Matt 21:9; cf. Luke 19:38)
Words of Institution: (see Mark 14:22-24; Matt 26:26-28; cf. Luke 22:17-20; 1 Cor 11:23-25)
"Take this, all of you, and eat of it, for this is my Body, which will be given up for you" (a combination of Mark 14:22; Matt 26:26; Luke 22:19; 1 Cor 11:24)
"Take this, all of you, and drink from it, for this is the chalice of my Blood, the Blood of the new and eternal covenant, which will be poured out for you and for many for the forgiveness of sins." (a combination of Mark 14:24; Matt 26:27b-28; cf. Luke 22:17, 20; 1 Cor 11:25)
"Do this in remembrance of me" (only Luke 22:19; 1 Cor 11:24a, 25b)
Memorial Acclamations:
"We proclaim your Death, O Lord, and profess your Resurrection until you come again." (cf. 1 Cor 16:22)
"When we eat this Bread and drink this Cup, we proclaim your Death, O Lord, until you come again." (cf. 1 Cor 11:26)
"Save us, Savior of the world, for by your Cross and Resurrection you have set us free." (cf. Matt 8:25; Luke 4:42; Rom 8:21)
Lord's Prayer:
"Our Father in heaven..." (Matt 6:9-13; cf. Luke 11:2-4; Mark 14:36; Gal 4:6)
Embolism: "Deliver us, Lord, we pray, from every evil... as we await the blessed hope and the coming of our Saviour, Jesus Christ" (Titus 2:13)
Doxology: "For the kingdom, the power, and the glory are yours..."
(found only in some biblical manuscripts after Matt 6:13; cf. Rev 4:11; 11:15; 1 Chron 29:11)
Greeting of Peace:
"Lord Jesus Christ, you said to your apostles, 'I leave you peace, my peace I give you'" (John 14:27)
"The peace of the Lord be with you always." (cf. John 16:33; 20:19, 21, 26)
Breaking of the Bread:
"Lamb of God, you take away the sins of the world..." (cf. John 1:29, 36; Rev 5:6-13; 22:1-3)
Preparation before Communion:
"Behold the Lamb of God, behold him who takes away the sins of the world. Blessed are those called to the supper of the Lamb." (John 1:29, 36; Rev 19:9)
"Lord, I am not worthy that you should enter under my roof, but only say the word and my soul shall be healed." (Matt 8:8; cf. Luke 7:1-10)
Concluding Rite:
Final Blessing (cf. Gen 28:3; Deut 14:29; Num 6:23-27; Ps 29:11)
Dismissal:
"Go forth, the Mass is ended."
"Go and announce the Gospel of the Lord." (cf. Mark 16:15)
"Go in peace, glorifying the Lord by your life." (cf. Ps 115:1; 1 Cor 10:31; 2 Thess 1:12)
"Go in peace." (cf. Exod 4:18; Deut 10:11-13; Judg 18:6; 1 Sam 1:17; Mark 5:34; Luke 7:50; 8:48) source
For more in-depth study visit these websites:
Strategies of the Jehovah's Witnesses
"Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect" - 1 Peter 3:15
