Bhaktivinoda Thakura describes 6 kinds of surrender, he says –

“anukulyasya sankalpah pratikulyasya vajranam
raksisyatiti visvaso goptrtve varanam tatha
atma-niksepa – karpanye sad-vidha saranagati. ”

There are 6 kinds of saranagati. “anukulyasya sankalpah”, whatever is favourable to Krishna and to execute Krishna Consciousness, we must accept that immediately.
In order to stretch this saranagati, the second word he is saying is just the opposite, “pratikulyasya varjanam”.
“pratikulyasya varjanam”, means which is not favourable. “Pratikul”, to execute Krishna Consciousness, to render service to Krishna or a devotee. Whatever is “pratikul”, whatever is not conducive for spiritual life and spiritual subject matter, we must give that up immediately.
So this in itself is a very very high level of surrender to Krishna.
Just imagine a husband and a wife, if wife gives up everything that husband doesn’t like and wife accepts everything or does everything that husband likes. Imagine how elevated that couple will become.
On the contrary, if wife does exactly the opposite of what husband wants and wife doesn’t accept everything that husband likes and rejects everything that he likes.
Same thing with husband, he doesn’t do, what wife likes and does what wife doesn’t like. What kind of surrender it is on both parts?
So surrendering to Krishna means we must accept everything that He likes, immediately,without waiting for a second and we should reject everything that He doesn’t like, immediately.
So this is called surrender, “ anukulyasya sankalpah  pratikulyasya varjanam”.
The third saranagati, Bhaktivinoda Thakur describes is “raksisyatiti visvaso”, to have full confidence, full faith that Krishna will protect me under all circumstances. This is Krishna’s promise to His devotees.
“Kaunteya pratijanahi na me bhakta pranasyati”.
“Hey Arjuna, boldly declare that my devotees , they never perish. ”
So “ goptrtve varanam tatha”, “That Krishna is my guardian, provider, He will provide me everything.” He is providing to rakshas, He is providing to animals in jungle, definitely He will provide to His devotees.
So to have a strong faith that Krishna, He will provide, that is “goptrtve varanam tatha”.
And last one is “atma-niksepa”. Last but not the least, “atma-niksepa”, means consigning everything that belongs to us.
There is a very good example of Bali Maharaj, he gave everything to Krishna, including himself. He gave the kingdom of the whole universe, not just Earth planet to Vamadev, who is Krishna. In turn what Krishna did, Krishna became so indebted, became so obliged that He became Bali Maharaj ‘s security guard. Such is the attitude of Krishna towards His devotees, who totally surrender to Him.
Even Gopis, Gopis were totally surrendered,
“Manasa deho geho yo kichu mor, apilu tuya pade nanda kishor”
Anything and everything that Gopis had, Gopis consigned that to Krishna.
So Krishna protects, He gives Himself to His devotees. And Krishna says to the Gopis – “I cannot repay the debt to you, you have given me everything.”
Krishna got defeated for eternity, He becomes sold out to Gopis. Krishna remains indebted to Gopis for eternity, He could never repay the debt of the Gopis. Why? Because Gopis did “atma-niksepa”, they consigned everything to Krishna.
Lord Ramchandra told Hanuman that even if I try to repay you for your love and devotion to me, I can never do that.
So this saranagatih, “atma-niksepa – karpanye”.
“Karpanye” means utmost humility. Humility means- “ I am spirit soul and my only duty is to serve Krishna and nothing else.” This is utmost humility.
So to offer that to Krishna is saranagatih.
One of the saranagatih, if not all, is good enough to surrender to Krishna.
This is called surrender and how to surrender to Krishna.