Say ten times:
اللَّهُمَّ صَلِّ وَسَلِّمْ عَلَى نَبَيِّنَا مُحَمَّدٍ
O Allaah, send prayers and peace upon our Prophet Muhammad.
Allahumma salli wa sallim 'alaa nabiyyinaa Muhammadin
The Prophet saw said: "Who recites blessings upon me 10 times in the morning and 10 times in the evening will obtain my intercession on the Day of Resurrection".
At-Tabrani, Sahih at-Targhib wa at-Tarhib 1/273.