Food incl liquids very often gets stuck in my 3 yrs old son's throat. some times it is really bad. what can i do ? any special precautions?

See your doctor: Abnormal swallowing in children is not common and so I would talk to your doctor. The test to do is a swallow study to look for anything wrong in the swallowing tube or esophagus. In general thicker foods seem to go down easier but this is not always the case- another helpful person is an occupational therapist or feeding team- both should be available at a local Children's hospital

Dysphagia: Dysphagia or trouble swallowing can sometimes be concerning for eosinophililc esophagitis (EoE). Symptoms of this condition include food impaction, with persistent trouble swallowing, abdominal pain, vomiting, or heartburn that fails to respond to medical therapy. See gastroenterologist or allergist for further workup and evaluation to determine if this is the possible cause. Likely needs scope