Srila Prabhupada explains how to avoid taking birth in lower life forms.
One who commits sinful activities because of ignorance, tamo-guna, obtains a lower body. Karanam guna-sango 'sya sad-asad-yoni janmasu (Bg. 13.22). There are hundreds and thousands of different species of life. Why are there higher and lower bodies? One receives these bodies according to the contaminations of material nature. If in this life one is contaminated by the mode of ignorance and sinful activities (duskrti), in the next life, by the laws of nature, one will certainly get a body full of suffering. The laws of nature are not subservient to the whimsical desires of the conditioned soul. Our endeavor, therefore, should be to associate always with sattva-guna and not indulge in rajo-guna or tamo-guna (rajas-tamo-bhavah [SB 1.2.19]). Lusty desires and greed keep the living entity perpetually in ignorance and prevent him from being elevated to the platform of sattva-guna or suddha-sattva-guna. One is advised to be situated in suddha-sattva-guna, devotional service, for thus one is immune to the reactions of the three modes of material nature.
SB 10.1.39 purport