Here are some signs that babies display when they are tired: For newborns (birth to 6 months; infants (up to 3 months) usually gets tired after being awake for more than 1-1½hours, and infants (up to 6 months) usually gets tired after being awake for more than 1-3hours) - pulling at ears - closing fists/clenched firsts - fluttering eyelids - jerky arm and leg movements - yawning - grimacing or a worried/painful look on your child’s face - arching backwards - difficulty focusing (baby might even go cross-eyed or seem to be staring into space) - sucking on fingers (this could be a good sign and might mean that the baby is trying to find ways to settle to sleep) For babies (6 to 18 months; babies (6 to 12 months) usually gets tired after being awake for more than 2-3hours, those up to 18months usually gets tired if they missed their afternoon naps) - clumsiness, bumping into things, falling over, spilling things more than usual - clinginess - grizzling - yawning - fussing, crying, whining, screaming - rubbing eyes or nose - demands for constant attention - boredom with toys - fussiness with food Compiled from: http://www.babycareadvice.com/babycare/general_help/article.php?id=32 http://raisingchildren.net.au/articles/is_my_child_tired.html Recognizing signs of tiredness could help allow parents to settle their babies at the right time. This will help babies fall asleep more easily and allow them to get better rest.
For me personally, it was very visible on his eyes. His eyes would be slightly droppy and sunken, and he would rub his eyes a lot. He would be fussy. These are the usual tell-tale signs for me and most of the times I am right
For newborn the obvious signs are yawning, look away from you or sight, rubbing his/her eyes and crying.