In this article we will explore some statements Prabhupada made regarding the look of a Vaishnava. We see today bhaktas wearing beard and long hair. At the beginning many people from the hippie community had also not shaved up but later the devotees became fame for clean-shaven hair.
“The words bhadra karāñā are significant in this verse. Due to his long hair, moustache and beard, Sanātana Gosvāmī looked like a daraveśa, or hippie. Since Śrī Caitanya Mahāprabhu did not like Sanātana Gosvāmī’s hippie features, he immediately asked Candraśekhara to get him shaved clean. If anyone with long hair or a beard wants to join this Kṛṣṇa consciousness movement and live with us, he must similarly shave himself clean. The followers of Śrī Caitanya Mahāprabhu consider long hair objectionable. Sanātana Gosvāmī was saved from a hellish condition (Mahāraurava) by the grace of Śrī Caitanya Mahāprabhu. Mahāraurava is a hell wherein animal killers are placed. In this regard, refer to Śrīmad-Bhāgavatam (5.26.10-12).”
Letter to: Dhrstaketu — New York (17 July, 1976)
“[…] Unless absolutely necessary, one should keep head shaven and not allow the hair to grow long. If absolutely necessary, one can dress like an American gentleman, with short hair, but long hair is prohibited. The reason that one with long hair is not my disciple is because he is against the principle. Unless absolutely necessary one should keep hair short, and if necessary one can dress like an American gentleman with short hair. It is not expected that everyone will join. For that reason we can’t compromise. The tendency is there to be hippy. […]”
Here we have the instruction through guru and sastra that as disciple we have to be cautious not to become lazy and take it as a unnecessary thing to have e. g. tilak put on. If we want to be in the disciple succession we have to follow Him and do it.

When should we cut the hairs?
Letter to: Ramesvara — NEWSLETTER, 26 November, 1976
[…] Now for our practical life we are known all over the world as shaven headed, is it not? Now we are becoming hair-headed, we are forgetting shaving. Because there is a little leniency, immediately faulty things are creeping in. So we should be known as shaven-headed, not hair-headed. This is discrepancy. At least once in a month you must be clearly shaven-headed. On the bright fortnight, on the day of purnima, four days after ekadasi. Once in a month, in the bright fortnight we must be shaven-headed. […] And in the room after the lecture:

http://vanisource.org/wiki/Room_Conversation_–_June_26,_1975,_Los_Angeles?t=hl#terms=long%20hairs
Devotee (2): Then what does it mean to become disciple?
Prabhupāda: Disciple, if you don’t like, give it up.
Devotee (2): We do like it.
Prabhupāda: You have already given up.
Devotee (2): If we didn’t like it, we would not come here.
Prabhupāda: No, no. You have already given up. My disciples do not keep so many hair.
Devotee (2): Many of your disciples do.
Prabhupāda: No. I don’t accept that. You just this one circle, little. But those who are keeping big hairs, they are rejected from my disciples.
Devotee (2): All right. That is clearing some things up.
Prabhupāda: Yes.
Devotee (2): This is what we want to know.
Prabhupāda: Yes.
Devotee (2): Because then that is an unequivocal statement.
Prabhupāda: No. This is, that you can…, that anyone who is keeping hairs and not following the rules and regulations, they are rejected from second initiation.
Devotee (2): What if they are keeping hair but they are following the rules and regulations?
Prabhupāda: Then let them follow. That’s a good life. But from external features he must be a Vaiṣṇava.
Devotee (2): To get second initiation.
Devotee (1): Does that mean shaved head?
Prabhupāda: Caitanya Mahāprabhu, when His students used to come without tilaka, so He refused to see his face. He refused to see his face. He said it is a crematory ground.
Devotee (2): Why is that?
Prabhupāda: There is no “why.” If you accept it, accept. If you don’t accept, leave us. Leave us. There is no “why.”
Devotee (2): Then that is…
Prabhupāda: You are not following strictly. You cannot ask why.
Devotee (2): We could not ask why when we were following strictly either, Prabhupāda. So I’m sorry that it has to be this way.
Prabhupāda: No, our thing is that we have got some principles. If anyone cannot follow, then we don’t accept him.
Devotee (1): Then what do you do with the rest of the world, except for the few people who…
Prabhupāda: So what I can do I am doing. Therefore you have no right to ask me. What is possible by me, I am doing. And those who are able to follow, they are following. That’s all.
Devotee (2): But they cannot engage anyone else. How can you reach the intelligent class?
Prabhupāda: So that is their business. That is not your business.
Devotee (2): We are trying to be disciples, so we considered it our business because we are sincerely trying.
Prabhupāda: So why you are bothering me? You do your business.
Devotee (2): Because from you only…
Prabhupāda: I do not accept you, because you are keeping hairs.
Devotee (2): I did not know that.
Prabhupāda: Yes.
Devotee (2): You never told me that in Hawaii.
Prabhupāda: Now I say, I’ll repeat that anyone who is keeping long hairs, he is no more my disciple.
Devotee (2): All right.
Prabhupāda: This is the first condition.