Place 1 inch of gravel at the base of each 5-inch pot. Mix 2 parts sterilized potting soil and 1 part coarse sand or perlite in each pot. Herbs needs a well-drained soil that is not too rich. Add 1 tsp. lime to each pot to sweeten the soil.
Place your parsley, basil and rosemary on a south or west facing window, and ensure they receive plenty of sunlight. Install a fluorescent grow lamp during the winter; lack of light is the most common reason that indoor herbs do not survive the cold, dark months.
Water your herb plants according to each herb's specific needs. Avoid getting the roots too soggy. Water parsley and basil deeply once per week during the growing season. Let your rosemary plant's soil dry completely, then water it generously.
Fertilize parsley, basil and rosemary with a liquid fertilizer at half the label recommended strength every four to six weeks during the growing season.
Prune parsley by cutting the leafy stalks close to the stem. Snip fresh basil leaves as they are required; if whole stems are needed, cut immediately above a pair of leaves. Prune plants periodically during the growing season to encourage new growth and maintain a high quality yield.
Look out for powdery mildew on your indoor plants, particularly rosemary. Powdery mildew is caused by a lack of air circulation. Run a 3-inch fan for three to four hours per day. Spray plants regularly with an insecticidal soap if you spot aphids or spider mites.