Teething happens typically between 6 months and 1 year. The top or bottom two front teeth come in first followed by the opposite teeth. Next is the molars. Here is a link to a tooth eruption chart from the ADA. Sometimes teeth eruption is delayed in the case of syndrome such as Down syndrome or cleidocranial dysplasia.
There are many symptoms attributed to teething: fever, pain, irritability, sleep issues, mouthing, drooling, red cheeks, decreased eating/drinking, gum irritation and diarrhea. In scientific studies only issues related to the mouth and low grade fever (under 102) have been proven. (1)
There are numerous remedies used for teething – some of which are harmful. I typically advise against teething rings filled with liquid or gels. These can leak their filling or leach plastic chemicals when placed in the mouth. They are also difficult to disinfect without breaking down the plastic. Benzocaine gel can interact with the blood and cause a condition called methemoglobinemia where the baby can turn blue ! Amber necklaces are choking hazards. Homeopathic teeth tablets have been found to have belladonna in toxic amounts and have caused seizures. The only thing I typically recommend is placing several wet washcloths in the freezer and letting the infant gnaw on them for relief. If solids have already been introduced then pieces of frozen banana or bagel can be given. If sleep is disturbed due to pain acetaminophen can be given or ibuprofen is the infant is over 6 months old.
The first dental visit is often advised around 1 year of age. Once teeth are erupted they can be wiped with a wet washcloth for cleaning. This cleaning is especially important before bed as sugar from milk/formula can cause tooth decay. Here is a link to a Q&A on teeth from the American Academy of Pediatric Dentists.
(1) L Markman. “Teething”. Pediatrics in Review August 2009.