From Sri Chaitanya Charitamrita:

A pure devotee is:

(1) Merciful, Kind  :

Kind to all the living beings, not only humans.

(2) Not defiant, Humble :  

Respects all, does not expect honours.

(3) Truthful :   

Acts only in the interests of Krishna, not in his own interests.

(4) Equal to everyone :

Sees Krishna in all the living beings and hence treats all as equal.

(5) Faultless :  

Surrendered to Krishna in words, deeds, and mind

(6) Charitable :

He has a magnanimous mind to distribute love and wealth to the needy.

(7) Clean : 

He is pure from material contaminations.

(8) Aware of the ownership of Krishna:  

Sees everything as Krsna's property.and engage everything in Krsna's service.

(9) Cares the welfare of everyone :  

Welfare work of a devotee for the benefit of all living entities.

(10) Peaceful :   

Not materially, but, really peaceful realising his relationship with Krsna.

(11) Fully Surrendered to Krishna :

He is totally dependent on Krishna entrusting himself to Krishna.

(12) Desireless :

He does not have any material desire anymore and his only desire is to serve Krishna and the vaishnavas including guru.

(13) Indifferent to material acquisitions : 

He engages everything he has including money and things in the service of Krishna.

(14) Fixed in Krishna consciousness :  

He can not be diverted by any means, from his devotion to Krishna.

(15) Self Controlled:

He controls all the six bad qualities, such as lust, anger, greed, illusion, madness and envy by engaging in Krishna's service.

(16) Moderate in eating :

He does not eat more than required as said by Krishna in Bhagavad Gita.

(17) Sane:

He is not obsessed with material things and he leads a simple life with basic needs only.

(18) Respectful :  

He respects all as parts of Krishna and does not expeect respect from others.

(19) No false prestige :  

He does not add materials to gain false prestige from others. He sees everything belongs to Krishna.

(20) Grave :

He is constantly thinking of Krishna and the real purpose of life, ie, serving the Lord and vaishnavas..

(21) Compassionate:

Compassionately distribute Krishna to everyone.

(22) Friendly :  

He is the friend to all like Krishna considers all as friends.

(23) Poetic :  

Because he always links everything with Krishna.

(24) Expert :  

Since he gains strength from his guru and Krishna, he is expert in performing anything for Krishna.

(25) Silent :  

He speaks only about Krishna and spiritual topics.  Not mundane things.

(26) Mild: 

Since he is satisfied in Krishna, he is always unagitated,  peaceful and mild.