Unfortunately, misinformation abounds.
If the battery is fairly fresh (and there's no way for even the phone manufacturer to tell that), you can start using it immediately. If not, you have to condition it - 3 full charges, each followed by 3 full (down to the point that the phone shuts off) discharges. After that you just make sure to charge it before it drops below 40%. (Dropping to 30% regularly drops the life by about 25%.)
This has nothing to do with Nickel technology, which was completely different (fully discharge every few cycles, etc.) Lithium has no memory, but it DOES lose conditioning if it sits on the shelf too long (many months), and even a new phone may have a battery made of old cells.