Cursing is something you "pick up" from other people through conversation,TV, and movies...very unnecessary, but something you think "everyone is doing it", so I will also. It is and becomes a very bad habit to break. It becomes wasted words, as Soldier said, "...when someone doesn't have anything else better to say". I don't watch movies now for that very reason...some would be very good movies, but the language used takes away from the plot and just show corruptness to the audience.
Cursing and slang words should cause a Christian to "shiver" rather than laugh or participate. We have remained silent on this for too long and have become participates ourselves. No wonder why some sinners say, "If so and so is a Christian, I want no part of Christianity, for he/she is no different than I." We are ambassadors(representatives)of Christ to the world and we need to represent HIM, not ourselves before the world; therefore, we need to talk, walk, and dress Godly, yes different from the styles/conforms of the world.
It is better to "think before you speak"...this gives you time to be aware of what you are saying before it is out. This is why many say "count to ten", when you become mad or upset...I'm sure that would help.
Commit Scriptures to memory: Ephesians 5:4, "Neither filthiness, nor foolish talking, nor jesting, which are not convenient: but rather giving of thanks." Psalm 19:14,"Let the words of my mouth, and the meditation of my heart be acceptable in thy sight, O LORD, my strength, and my redeemer." Psalm 150:6, "Let everything that hath breath praise the LORD, Praise ye the LORD." Colossians 3:8, "But now ye also put off all these; anger, wrath, malice, blasphemy, filty communication out of your mouth." Ephesian 4:22, "That ye put off concerning the former conversation of the old man, which is corrupt according to the deceitful lusts;" Hebrews 12:1, "Wherefore seeing we also are compassed about with so great a cloud of witnesses, let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us." When we commit Scripture to memory, we are able to use it in a way that benefits us when we face temptation of any manner. Psalm 119:9,"Wherewithal shall a young man cleanse his way? by taking heed thereto according to thy word." Psalm 119:11, Thy word have I hid in mine heart, that I might not sin against thee." Reading the Scripture has a way of cleansing us from within, then the filthy conversation will not be there to come out...it will be replaced with something better that will help you grow and mature in your Christian life. Always remember to pray for GOD'S help in all things and thank HIM when you have been successful getting over any hurdles, no matter how small or insignificant they may seem at the time.
Depend upon GOD and HIS word to help you, not your friends unless you are making them accountibility partners, but remember you will always be 100% accountible to GOD for what you say, think and do.