When people had difficulty accepting Jesus’ teaching and they began to walk away from him, Peter and other disciples remained. They stayed not because they found his words easy to accept but because they recognized in him the source of eternal life (John 6:68).
It is that desire for truth that leads to eternal life which fundamentally guides our quest of faith as well.
There can be lots of superficial reasons that may attract us to a particular religion or denomination (leaders, customs, heritage, particular ministries, relationship, familiarity, etc.) but it is the search for truth that is most important.
Accordingly, a person should look for signs of an authentic experience of God. Those will include challenging divine revelation and an invitation to personal holiness manifested in a transformed life. One may even consider exploring how a particular religion or denomination experiences these signs in a historical, consistent, integrated way.