We were instructed to right away. Start off with baby laying on your chest (these are the best snuggles!) and as Baby's head control starts to develop, you can start putting him/her on the floor to play. There is no specific age, since every baby is different. My two-month-old was born with a strong neck (according to the nurses, anyway) and was able to look around right away, but some babies aren't able to do that for awhile.
Keep in mind that Baby probably won't be a big fan of it, so you should start with small spurts. My guys gets about five minutes on the ground with me laying next to him before he gets too mad. Make sure you're not leaving your little one unattended, though, especially if s/he can't turn their head!
at 4:29 PM on Nov. 10, 2008