Sheytaan uses six ways to lead us astray. Hazrat Suleymaan Suri (RA) says:
"Sheytaan loves innovation(in deen) more than sinfulness and impiety. If he can't bring a person to innovation(in deen), he makes him greedy for different kinds of mortal sins. He makes them so tempting and orates them for the person. If he(sheytaan) cannot control someone by this way and faces resistance then he brings that person towards minor sins. He lowers their importance so much so that person gets stuck in the web and gets used to of them. And this makes him brave for attempting on mortal sins. If this technique also fails then he(sheytaan) advices him on those acts which have neither punishment nor reward. This way, sheytaan succeeds in wasting our precious time which could have been spent in worshipping Allah (ibadah). If sheytaan fails in all of above methods he busies the man in futile efforts. So that man leaves the continuous efforts in way of Allah and falls into rest & ease. This way, sheytaan keeps on trying and trying until he succeeds. Allah Subhana wa Ta'la has blessed us with sense & understanding and we can save ourselves only with strong determination; because our enemy (sheytaan) is determined.
In Quran Karim, Allah ta'ala has prompted one thing in the creation of Hazrat Adam (A.S.); he(sheytaan) rebelled and asked for time to lead mankind astray and vows to do this no matter what.
At another place, when Allah ta'ala talks about slip of Hazrat Adam (A.S), He (Allah Subhana wa tala) relates it towards sheytaan. He is responsible for this slip and not Hazrat Adam (A.S.)
But Satan caused them to slip out of it and removed them from that [condition] in which they had been. And We said, "Go down, [all of you], as enemies to one another, and you will have upon the earth a place of settlement and provision for a time."(Al Baqarah:36)
But Satan whispered to them to make apparent to them that which was concealed from them of their private parts. He said, "Your Lord did not forbid you this tree except that you become angels or become of the immortal."(Al Ayraaf:20)
"Then Satan whispered to him; he said, "O Adam, shall I direct you to the tree of eternity and possession that will not deteriorate?" (Taha:120)
Sheytaan initiated his enmity towards Hazrat Adam (A.S.)(and thus, mankind) by putting doubt in his heart. He took him (Hazrat Adam A.S.) towards such a thing from which Allah ta'ala had clearly forbidden him, i.e. towards doubt. This doubt is the main weapon and a main instrument for which he(sheytaan) asked for time; to mislead us from right path and will stop us from Truth.
How does he put doubt in hearts? We'll find it out in next part Inshallaah.