رَبَّنَا آتِنَا فِي الدُّنْيَا حَسَنَةً وَفِي الْآخِرَةِ حَسَنَةً وَقِنَا عَذَابَ النَّارِ
Rabbana atina fid-dunya hasanatan wa fil-akhirati hasanatan wa qina 'adhaaban-nar
Our Lord, give us good in this world and good in the Hereafter, and protect us from the punishment of the Fire.
Comprehensive dua that can be said before salam or anytime
This was the most frequent dua of the Prophet (PBUH), asking for good in both worlds.