I do believe in transmigration (reincarnation). We've been reborn countless times at all levels. Our bodies die, our soul NEVER dies.
At the moment of death, depending on your final thoughts (positive or negative) is where you will go. If you are filled with love, kindness and compassion, you will have a better rebirth.
It is also helpful to think of spiritual masters and teachers so you will be welcomed by them.
Likewise if you are filled with attachments (worries, remorse, jealousy, anger, guilt, grudges against someone, objects etc) being unable to let go of anything at the moment death.. These kind of negative thoughts are detrimental to us.
If you have recently lost a loved one, it is highly important to refrain from a consuming a carnivore diet, otherwise you will further delay their human rebirth, prolonging their suffering. We must not harm ANY living beings which also includes animals and even insects.
Whether anyone choose to believe in it or not is their own free will. After death, there is no free will. It would be too late to change anything.