The most common method of increasing the charm skill is to practice in front of a mirror - the "rehearse speech" function. You will need this skill very much during interactions with other Sims. A charismatic Sim tells funny jokes, can give other Sims cute compliments (after researching attraction level 3), gracefully apologize (after level 4), flatter (after level 6), and charmingly introduce themselves (after level 8).
Having, however, a level 7 attraction, you can borrow a small amount of funds from a peace-loving Sim (500 play money), and from level 9 you can ask for a huge loan instead of this (2000 play money). However, once you reach level 10, you can use an even more cute option - ask your boss for a promotion (the speech must be done over the phone). This will allow you to make a better assessment of labor and get a currency reward.
