If the plant has become root-bound it will be necessary to cut and unwind any roots that circle the plant, otherwise the roots will never develop normally. If the old soil surface has accumulated salts, the top inch should be removed. Set the rootball in the middle of the new soil. Fill soil around the sides between the rootball and pot. Do not add soil above the original level on the rootball, unless the roots are exposed or it has been necessary to remove some of the surface soil.
Leggy plant needs to grow bushier, keep more compact form.
Pinch out growing tip of tallest stem, removing it close to the leaf point. New growth forms just below pinched-out tip, makes plant bushy. After watering and settling, the soil level should be sufficiently below the level of the pot to leave head-room. A properly potted plant has enough headroom to allow water to wash through the soil to thoroughly moisten it. This includes a number of minor care activities that distinguish the beginner from the more experienced indoor plant grower.