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 (s) 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 (s) 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."
 

Invite (mankind, O Muhammad SAW) to the Way of your Lord (i.e. Islâm) with wisdom (i.e. with the Divine Inspiration and the Qur'ân) and fair preaching, and argue with them in a way that is better. Truly, your Lord knows best who has gone astray from His Path, and He is the Best Aware of those who are guided.

Extracted from the writings of Ibn Qayyum Al-Jawziyyah