In general use a gritty, well drained compost and keep it moist but not soggy. Herbs do need very regular watering. Add a little gravel in the base of the planter to help with drainage.
Mediterranean herbs such as thyme, rosemary, lavender, sage, and oregano are not so fond of the British damp. They like a poor, almost sandy soil to thrive in, so use sand and pebble mulch around them to prevent rotting.
There are also a few herb ground-bullies that you need to look out for! Mints, lemon balm, and lemon verbena are notorious for taking over the whole patch if you let them. If you have them in your planter, pot these cheeky herbs inside their original pot to contain their roots.
What we want with herbs is leafy growth more than flowering, so use a balanced fertiliser rather than a potassium-rich one.
Do a little research on the herbs you decide to go for; some will last for years, but others die off every winter.
Remember, frequent harvesting from herbs is actually beneficial: snipping off the tips will push the plant to grow more quickly and compactly. Try to take an inch or two from the top of the stem above two leaves, which will then grow two new shoots.
And that’s all you need. So get your planters and get planting!