Laylatul Qadr — the Night of Power — is described in the Qur'an as better than a thousand months (Surah Al-Qadr 97:3). It falls within the last 10 nights of Ramadan, most likely on an odd night.
The Prophet ﷺ increased his worship and dua on these nights. He specifically taught Aisha (RA) the most perfect supplication: 'Allahumma innaka 'Afuwwun tuhibbul-'afwa fa'fu 'anni' (O Allah, You are Most Forgiving, and You love forgiveness, so forgive me).
Seek it in the odd nights: 21st, 23rd, 25th, 27th, and 29th of Ramadan. Increase dua, Qur'an recitation, Tahajjud prayer, and istighfar throughout all 10 nights.