That would depend...what do you need them for? The most common herbs can be purchased at the supermarket. Some stores even sell live herbs in the produce department. If you want to just go outside and look around,there are a few that are easy to spot. Dandelion is a very useful herb. Every part of the plant can be used for different things. Mint is another one. Pine too. Clover. The list goes on and on. Just make sure that you aren't grabbing something poisonous, especially if you will be ingesting it.
As has been said it very much depends on where you live and what you are close to.
In England there are different wild herbs than in Asia.
Most "common" herbs can be found in any supermarket in both fresh and dried forms, these can be used in food as well as in magickal practices.
Of course a trip out in the countryside will show you lots of native herbs but I would never recommend going out and using wild herbs for ingesting as there are chemicals, biological waste and you may be picking the wrong herb with severe consequences.
Always make sure you know which herb is which before using it, keeping a field guide of herbs is very useful, as is having a magickal guide like Scott Cunninghams Encyclopedia of Magickal Herbs, as many herbs have poisonous doppelgangers that live in the same environment with entirely different properties..
The most common as Rikki had also stated are dried ones you can find in your local super market. The one I buy from the super market are bay leaves. But it probably depends what your local stores carry.
Too add to this a bit, some of the most common that I've seen, in both dried and fresh forms, are parsley, dill, basil, mint, sage, and thyme. Depending on where you go, you can also find fresh, edible flowers like marigolds too.If you are looking for something specific, I'd call your local grocery store and see if they carry what it is you're looking for. You could also check your local plant nursery. They tend to have several varieties of herbs as well.
I would suggest you to look in your kitchen.You may find parsley,mint,basil,rosemary,thyme,sage,dill,rosehip etc.The list goes on the peppermint,clover,bay leaves,oregano,aloe are some of the easiest ones.You may want to read Scott cunninghams book on herbs.Its absolutely widespread describing the herbs.
Extremely receptive to most energy, ergo can be used as an interesting battery for energy, which you can probably release by burning, whether physically or astrally.
If you need details, it also comes with instructions. Just ask the grass.
