Shaytan knows our weak points thus we need to realize what they are as well. Just as a country will prepare its military to defend its weak points we must also prepare our army to defend our weak points against our Shaytan. A very effective dua against the Shaytan is:

‎اللهم إن إبليس عبد من عبيدك يراني من حيث لا أراه وأنت تراه من حيث لا يراك وأنت أقوى على أمره كله وهو لا يقوي على شيء من أمرك, اللهم فأنا أستعين بك عليه يا رب فإن لا طاقة لي به ولا حول ولا قوة لي عليه إلا بك, اللهم إن أرادني فأرده وإن كادني فكده, واكفني شره, وأجعل كيده في نحره برحمتك يا أرحم الراحمين, وصلى الله على محمد وآله الطاهرين.

“O Allah, Iblis (Satan) is one of Your creatures who sees me from a place that I cannot see him and You see him from a place that he cannot see You, and You have power over all his affairs while he does not have power over any of Your affairs. Therefore O Allah, I resort to You for help against him, because O Lord (provider, nourisher, sustainer, the one who transforms potentiality into actuality) I do not have any capability against him, no power to change or force to enact, except through You. O Allah, If he intends evil for me, turn it back on him, and if he schemes against me then you scheme against him. Save me from his evil, and make his scheme to attach to his own neck. By Your mercy, O the most merciful of those who show mercy. May Allah bless Muhammad and his purified progeny.”