On a short haired dog it is easy. Just run your hands over the body and if there is a lump, check it out and see if it has little feet. Do not try to pull the tick out. Get help. Also, if the tick is a paralysis tick the back legs will drag and the dog will droop very quickly+ that is time to go to the Vet.
On a hairy dog, it is more difficult, you keep stroking the dog and again you may find a tick