Make Da'wah - Spread the word of Islam
Abu Mas'ud 'Uqba ibn 'Amr al-Ansari al-Badri reported that the Messenger of Allah, (PBUH), said, "Anyone who shows the way to something good has the same reward as the person who does it." [Muslim]
Ramadhan is the perfect time to make da'wah to Muslims who are not practicing Islam as well to non-Muslims.
For example if you encourage someone to go for Salah, or pay Zakat and the person actually goes ahead and prays or pays Zakat, Allah will reward him for the good deeds and at the same time give you (the one that encouraged them to do good) an equal reward as he has given them without decreasing what he gave them.
"Oh Allah allow us to make the most of Ramadhan. Oh Allah, let us meet you with a clean heart, with all our sins erased. Oh Allah grant us mercy, and make us from those that you have freed from hell fire."