Allaah has blessed the month of Ramazaan with numerous advantages and virtues over other months. This is the month in which the noble Qur'an was revealed. In one of the odd nights of the last ten days of this month is the Night of Decree, in which worshipping Allaah is better than worshipping Him for a thousand months. When Ramazaan begins, the gates of Paradise are opened, and the gates of Hell are closed. At the end of every night of Ramazaan, Allaah will forgive all the sins of those who really observed fasting in a proper manner, and rid them of every act of disobedience.
There is no Specific way of welcoming Ramazaan, but the Muslim should welcome it with joy and happiness and thanking Allaah for enabling him to reach Ramazaan, for He has caused us to be among the living who compete in doing righteous deeds. Reaching Ramazaan is a great blessing from Allaah. Hence the Prophet ﷺ used to give his companions the glad tidings of the arrival of Ramazaan by saying: “أَتَاكُمْ رَمَضَانُ شَهْرٌ مُبَارَكٌ” and explain its virtues, and the great reward that Allaah has prepared, whoever is deprived of its goodness is indeed deprived. Classed as Sahih by Shaykh Albani in Sunan Nasa’i 2106.
It is prescribed for the Muslim to welcome this blessed month with sincere repentance and preparations to fast and pray Qiyam, with a sound intention and sincere steadfastness.
Dua to read, sighting the new moon for Ramazaan OR any other month
" اللَّهُمَّ أَهْلِلْهُ عَلَيْنَا بِالْيُمْنِ وَالإِيمَانِ وَالسَّلاَمَةِ وَالإِسْلاَمِ رَبِّي وَرَبُّكَ اللَّهُ "
Allaahumma Ahlilhu A’laina Bil-Yumni Wal Eemani Was-Salamati Wal-Islami, Rabbi Wa Rabuk Allaah. Meaning: “O Allaah, bring it over us with blessing and faith, and security and Islam. My Lord and your Lord is Allaah. Classed as Sahih by Albani, Sunan At Tirmidhi 3451, Musnad Ahmad Vol2:366 and Sahih Ibn Hibban 888