I used a "method" with both of mine.
On Becoming Babywise maps out an order of things that happen for babies. They eat. They sleep. They are awake... and other than pooping, which they can do either awake or asleep, there isn't much else the first few months.
What OBB taught me, was to pay attention to the order of those 3 main things. Most people feed the baby to sleep, and when baby wakes up, then they have some awake time until baby is fussy, they feed baby to sleep again. According to OBB, if you feed them, keep them awake for a bit (over time this period of awake time gets longer and longer), THEN put them down for sleep they sleep better--and longer.
I followed this routine throughout the day, until bedtime. At "bedtime" you just omit the awake time. You feed baby, then put them right to sleep.
It can be a little bit of a challenge at first, and the "awake time" for a newborn is quite small. But it grows with baby. The eat/awake/sleep cycle for a newborn is around 90 minutes to 2 hours on average. As they grow, that cycle gets a little longer, with more minutes spent awake and more minutes spent asleep.
Both my babies slept for a minimum of 6 hours at night by 3 months old. The first one was completely breast fed only and took almost to 12 weeks to sleep that long. The second one we had to switch to formula around a month old. She slept 7 hours beginning at 6 weeks old.
And, I know you didn't ask specifically about putting them down at bedtime, but, we had all kinds of problems leaving my oldest when he was around 1 yr old, b/c he could climb out of his crib. Once he got to sleep, we were good.. no problems whatsoever. But he fought it and it was a tough road. But, by baby #2, I had discovered the Ferber Method (sometimes mistaken referenced as "cry it out"--which isn't what it really is)... and beginning sometime around 5- 6 months (which is what I believe is an appropriate and effective age) we used it with baby #2. In 3 nights, she was falling asleep in her crib, without me in the room, in less than 10 minutes, with zero crying.. and then sleeping "thru the night".
They are 12 and 15 years now. And still champion sleepers. No bedtime issues with them, or nighttime issues.