Preheat your oven to 175 Fahrenheit or 80 Celsius. This is a very low oven heat if you have a gas oven.
Depending on how many herbs you have, tine a baking tray or a sheet with baking parchment or greaseproof paper. You don't really need to use the paper, but it's easier to lift the herbs from the tray and it prevents it from getting any extra flavour (that might be on your tray from before)
If you picked your own herbs, you can use them as they are, but if you are not sure where the herbs came from, quickly run them under a water and rinse them.
You can either leave your herbs as they are or separate leaves from the stems. They will dry quicker this way.
Spread the herbs, so that they don't overlap on your baking tray.
Place in the oven and dry for about 10 minutes, then check them and move the herbs around, so that they dry more evenly.
Depending on what herbs you are using, you might need another 10 minutes. Depending on how quickly your herbs are drying, you might need an extra 5 minutes on the top of that.
Your herbs will be ready, when they are visible dry, but also rustle against the paper.
Leave the herbs to cool down in a room temperature first.
Lightly scrunch or crumble your herb leaves and store them in an airtight storage jar, like a jam jar with a lid.
Don't forget to label your container with the name of the herb and use within 3-6 months.
Notes
Dry herbs (when stored correctly) won't really go off, but they will lose their colour and flavour over time. It's best to use them within 3-6 months, but they will be perfectly fine for a few years.