Dr M Weissbluth's book, Healthy Sleep Habits, Happy Child, will help to figure this stuff out. At 2 mos, I asked my husband, what's the big deal about sleeping through the night? By 5 mos, I was desperate.
They start needing your help to sleep. Before this age, they will sleep when tired. Watch for signs that your baby is tired: rubbing face, ears, or eyes, starting to look a little glassy-eyed, or maybe yawning, maybe a little fussy. As soon as you seen the signs, lay the baby down to sleep (nurse, rock, or rub the back). If you are good at spotting the signs, you won't ever need CIO.
At this age, 3 naps, lasting an hour or so, and night time sleep (with wakings) from 6:30 PM to 6-7 AM is possible to achieve and needed. You probably won't have full night's sleep until 9 or 10 mos. Don't worry that daytime sleep will lead to less night sleep, this is a myth. Ditto for an early bedtime leading to early waking. They naturally wake at dawn no matter how tired.