Leviticus 11 outlines simple markers we can follow, provided we know enough about the animal in question.
Here's a simplified overview:
Land Animals: Have Divided Hoof & Chew the Cud
Leviticus 11:1 "ADONAI said to Moshe and Aharon, 2 "Tell the people of Isra'el,'These are the living creatures which you may eat among all the land animals: 3 any that has a separate hoof which is completely divided and chews the cud - these animals you may eat. 4 But you are not to eat those that only chew the cud or only have a separate hoof. For example, the camel, the coney and the hare are unclean for you, because they chew the cud but don't have a separate hoof; 5 6 7 while the pig is unclean for you, because, although it has a separate and completely divided hoof, it doesn't chew the cud. 8 You are not to eat meat from these or touch their carcasses; they are unclean for you." CJB
Leviticus 11:27 Whatever goes on its paws, among all animals that go on all fours, is unclean for youClean Guideline: The animal must have a divided hoof and chew the cud.
Clean Examples: cow, lamb, bison, deer, etc.
Unclean Guideline: An animal that has a divided hoof but does not chew the cud is unclean. Likewise, an animal that chews the cud but does not have a divided hoof is unclean. An animal with a hoof that is not divided hoof is unclean. An animal with paws is unclean.
Unclean Examples: pig, camel, horse, dog, cat, etc.
Water Creatures: Have Both Fins & Scales
Leviticus 11:9 "'Of all the things that live in the water, you may eat these: anything in the water that has fins and scales, whether in seas or in rivers -these you may eat. 10 But everything in the seas and rivers without both fins and scales, of all the small water-creatures and of all the living creatures in the water, is a detestable thing for you. 11 Yes, these will be detestable for you -you are not to eat their meat, and you are to detest their carcasses. 12 Whatever lacks fins and scales in the water is a detestable thing for you." CJBClean Guideline: anything in the water that has fins and scales
Clean Examples: salmon, cod, etc.
Unclean Guideline: a water creature without fins, a water creature without scales
Unclean Examples: lobster, shrimp, jellyfish, oyster, sea turtle, shark, etc.
Birds & Insects
Leviticus 11:13 "'The following creatures of the air are to be detestable for you - they are not to be eaten, they are a detestable thing: the eagle, the vulture, the osprey, 14 the kite, the various kinds of buzzards, 15 the various kinds of ravens, 16 the ostrich, the screech-owl, the seagull, the various kinds of hawks, 17 the little owl, the cormorant, the great owl, 18 the horned owl, the pelican, the barn owl, 19 the stork, the various kinds of herons, the hoopoe and the bat. 20 "'All winged swarming creatures that go on all fours are a detestable thing for you; 21 except that of all winged swarming creatures that go on all fours, you may eat those that have jointed legs above their feet, enabling them to jump off the ground. 22 Specifically, of these you may eat the various kinds of locusts, grasshoppers, katydids and crickets. 23 But other than that, all winged swarming creatures having four feet are a detestable thing for you." CJBClean Guideline: a winged swarming creature on all fours only if it has jointed legs above their feet to jump off the ground,
Clean Examples: locust, grasshopper, cricket, chicken, dove, turkey, etc.
Unclean Guideline: a winged swarming creature with four feet
Unclean Examples: barn owl, eagle, raven, vulture, seagull, etc.
Leviticus 11:29 "'The following are unclean for you among the small creatures that swarm on the ground: the weasel, the mouse, the various kinds of lizards, 30 the gecko, the land crocodile, the skink, the sand-lizard and the chameleon." CJB
Leviticus 11:41 "'Any creature that swarms on the ground is a detestable thing; it is not to be eaten - 42 whatever moves on its stomach, goes on all fours, or has many legs -all creatures that swarm on the ground; you are not to eat them, because they are a detestable thing. 43 You are not to make yourselves detestable with any of these swarming, crawling creatures; do not make yourselves unclean with them, do not defile yourselves with them." CJBClean Guideline: None are clean.
Clean Examples: None.
Unclean Guideline: a creature that swarms on the ground; a creature that moves on its stomach; a creature that goes on all fours; a creature with many legs
Unclean Examples: crocodile, gecko, snake, mouse, centipede
Avoid Carcasses of Clean Animals
Leviticus 11:39 "'If an animal of a kind that you are permitted to eat dies, whoever touches its carcass will be unclean until evening. 40 A person who eats meat from its carcass or carries its carcass is to wash his clothes; he will be unclean until evening." CJBClean Guideline: None are clean.
Clean Examples: None.
Unclean Guideline: any clean animal that has already died from natural causes or some other unknown cause
Unclean Examples: any clean animal, roadkill, etc.
"Be Holy, for I am Holy"Leviticus 11 ends with these memorable words:
Leviticus 11: 44 "For I am ADONAI your God; therefore, consecrate yourselves and be holy, for I am holy; and do not defile yourselves with any kind of swarming creature that moves along the ground. 45 For I am ADONAI, who brought you up out of the land of Egypt to be your God. Therefore you are to be holy, because I am holy. 46 "'Such, then, is the law concerning animals, flying creatures, all living creatures that move about in the water, and all creatures that swarm on the ground. 47 Its purpose is to distinguish between the unclean and the clean, and between the creatures that may be eaten and those that may not be eaten.'" " CJBFood for thought: Verse 47 (above) is especially important to keep in mind when trying to understand Scripture (namely the Brit Chadashah, or New Testament) because where "food" is referenced, it can only be referring to "clean meat" because "unclean meat" would never be considered as food by someone with a Hebrew / Jewish mindset.