Babies should begin teething and growing their first teeth by age 4 to 7 months.
And signs that your baby is teething and those teeth are growing in are drooling, grabbing his/her ears, bulging or swollen gums, trouble sleeping, irritability, chewing, sucking and trying to bite everything they can, rubbing their face a lot and rejecting food, refusing to eat and you should also notice a little tooth showing up in the babies gums where there wasn't any tooth before.
Babies who're teething may also run a fever and have diarrhea and the diarrhea can cause diaper rash.
The baby may also get a rash on his/her face from the drool when teething so wipe the drool off the babies face often.