1. Unnecessary Talking
Umar Ibn al-Khattab, may Allah be pleased with him, said: "A person who talks too much is a person who often makes mistakes, and someone who often makes mistakes, often has wrong actions. The Fire has a priority over such a frequent sinner."
2. Unrestrained Glances
It has been related that the Prophet Sallallahu Alaihi Wassallam once said words to the effect: "The glance is a poisoned arrow of Shaytan. Whoever lowers his gaze for Allah, He will bestow upon him a refreshing sweetness which he will find in his heart on the day that he meets Him."
3. Too Much Food
Al-Miqdam ibn Ma'd Yakrib said: "I heard the Messenger of Allah say: "The son of Adam fills no vessel more displeasing to Allah than his stomach. A few morsels should be enough for him to preserve his strength. If he must fill it, then he should allow a third for his food, a third for his drink and leave a third empty for easy breathing."
4. Keeping Bad Company
Allah's Apostle said: "The example of a good companion (who sits with you) in comparison with a bad one, is I like that of the musk seller and the blacksmith's bellows (or furnace); from the first you would either buy musk or enjoy its good smell while the bellows would either burn your clothes or your house, or you get a bad nasty smell thereof."
Extract from the book "Purification of the Soul"
By Ibn ul Qayyum al Jawziyya, Imam Abul Hameed al Ghazali and Ibn Rajab al Hanbali.