Vomiting

Puppies from time to time do vomit their food, especially if they just eaten their meal in 2 seconds flat. Sometimes after a worming tablet has been given it may put the dog off his food for a day.
Eating small amounts during this period.

Since the above mentions bolting his food or a worming tablet, we can guess that this is the cause. However if none of these items apply we are dealing with the unknown. Has he eaten something from the garden that did not agree with him, or is it a lot more serious.

ACTION, Telephone the vet and try to give him as much information as possible;
'I Just fed him and he was running around playing'... In most cases he will pick up where he left off.
It is the fear of the unknown ,that a vet should be contacted, if you do not know what the cause of the vomiting is, Telephone the vet immediately and ask for further advice.

If the dog is seen to swallow a known poison 'While someone telephones for help' induce vomiting by giving a solution of salt water (1 Teaspoonful in a tumbler of water for an average sized dog) Only give milk if the substance swallowed is at all corrosive. Never do this more than once, and not at all if the dog is un-conscious. Get the dog to a vet immediately taking with you the poison or its packaging.