Du'aa for fear of Shirk (attributing any partner with Allah in worship)

اللّهُـمَّ إِنّـي أَعـوذُبِكَ أَنْ أُشْـرِكَ بِكَ وَأَنا أَعْـلَمْ، وَأَسْتَـغْفِرُكَ لِما لا أَعْـلَم

O Allah, I seek refuge in You lest I associate anything with You knowingly, and I seek Your forgiveness for what I know not .

 
[Ahmad 4/403. See also Al-Albani, Sahih ul-Jami' As-Saghir 3/233 and Sahih ut-Targhib wat- Tarhib 1/19]