It's very difficult to predict if dog has fever or not unless you take him to the vet. You can certainly predict that puppy is unwell by the unusual behaviour he exhibits. For example, everyday you come from office, your puppy comes to you jumping and waging his tail. One day, you find him just sitting at the corner and weakly waging his tail. Something is wrong! Everyday your dog wakes up at around 6-7 AM inthe morning. One day, you find him sleeping late till 8am. Again, somethig is wrong. Your puppy refuses to eat his favourite meal. He's excessively vomiting. You find loose stools. All these are the indictions that the puppy is not doing well.
Whenever, you find your dog exhibiting a behaviour very unsual of him, it's best to take him to the vet right away rather than letting things go out of the hand. Also, never feed human medicines to your dog unless you know how to administer them on the dog.