You have to check the morphology of snake.

Check the shape of head, shape of eye pupils, and presence and absence of fangs. Usually snakes with rounded heads are non venomous while as triangular head snakes are venomous.

1- It is confirmed that the snake is poisonous by color because the bright colors indicate the toxicity from the size of the snake. also, If it is small, it is poisonous from the shape of the pupil

2- The most common enzymes in snake venoms are Phospholipase A2, Serine proteases, Metalloproteinase, Acetylcholinesterase, L-amino acid oxidases, Nucleotidases, and Hyaluronidases.

3- antivenom treatment

You should never use only the animal's morphology or color, these are very variable factors, depending on location, species and other factors. For example, we have in Brazil venomous snakes with rounded head and pupils, so these characteristics are very variable. To recognize whether the species is venomous or not, it is important to know the venomous species in your region and specific morphological characteristics (presence of loreal pit, rattle, etc.) that can indicate more effectively whether the animal is venomous or not. Color and simple morphology are definitely not good options for this type of identification.

It is important that you know the venomous species in your locality and know the symptoms that each venom can elicit. Another example from Brazil, is easily recognizable which type of accident caused by snake by the symptoms that the patient presents if you know the venomous snakes and the symptoms. It is interesting that you consult medical guides to know the symptoms that the venom of each snake can cause.

About identifying the nature of the venom, it is a somewhat contradictory matter, there are some diagnostic methods based on recognizing proteins at the site of inoculation or in the plasma, but these methods have not been very widespread due to often the effects being quick and there are no time to access the samples, in addition, the results may be unreliable.

About the treatment, the best treatment is always the one indicated by the doctor and it depends a lot on what is recommended for each region. In Brazil, serum therapy is widely spread, but unfortunately not all places have this feature. Treatment depends a lot on the type of accident, the severity that develops and the time between the bite and the start of treatment.

The WHO has very interesting guides and information regarding the management of accidents with venomous snakes. It is worth taking a look.

Thanks to all for updating me on the matter. As Dr Priscilla very rightly said that the animal morphology varies from region to region in addition to that majority cases where bringing snake to hospital is not possible by relatives. Further, my query - Is any harm by administering ASV in all suspected cases of Snake bites?

Yes, there is a big risk. In fact, antiophidic serotherapy is specific for the snake genus, sometimes even for the species, since there is great variation in venoms between genera and species. Since serum is made from heterologous protein, the risks of non-specific/necessary use of serum involve early (anaphylactic shock) or late (hypersensitivity, serum sickness) adverse reactions. These effects can be very serious and depend on a series of factors intrinsic to the patient and others related to the administration of the serum, amount, quality and purity of the serum, etc. In a context of envenomation in which the causative agent is known and the need to use the serum is identified by the severity of the accident, the benefits far outweigh the risks, but outside this context, administration to all suspected patients can be really dangerous.