This info is for the annual Basil, not he perennial type as far as I can tell.
Needs
Unlike e.g. Thyme, Basil needs fertile well drained soil and regular watering. Self-watering pots may be indicated. Requires full sun or partial shade. Does not easily tolerate temperatures below 10 degC. When watering, avoid showering the leaves and stems.
Harvesting
Up to a third of a plant can be harvested at once, but do fertilise after a heavy harvest. Harvest the top leaves first. Be sure to nip flowering stalks, as the plant will loose vigour if allowed to flower. Does not dry well. Can be pureed with a bit of water and frozen in ice cube trays, or frozen whole if coated with olive oil on both sides.
Make plants bushy by pinching off the top two pairs of leaves once a stalk reaches a reasonable height. The more you do this (without overdoing it), the more new shoots the plant will send out, becoming bushy instead of tall and sparse. You end up with more plant overall.
Propagation
From seed. Should germinate in about 7 days, avoid the seeds/seedlings getting cold.
Seed can be harvested by allowing some flowers to grow. The petals will drop, leaving behind a carpels that contain the seed. These are initially green, and should be left till they are brown. The seeds can then be harvested out of these pods.
Uses and Companion Planting
Basil apparently keeps flies, aphids and other pests away. Recommended companion for tomatoes and summer savory. Basil may fill the pot with fibrous roots, possibly challenging other plants as it matures.
Sources
1, General 2, General 3, General 4 5, Growing 6, Harvest seed 7, self-watering 8, Daves Garden