when to harvest ?

I have the following herbs that are either blooming or getting ready to bloom. How do I harvest the seeds?

Basil - Thai - ready to bloom
Italian Oregano in gorgeous bee-tempting bloom
Lavender - blooming
Thyme - nicely blooming, one is golden the other, regular
Tarragon (does it bloom?)
Arugula - blooming now, (bolting?)
Mustard greens - bolting and seeding in pods
Cilantro - just coming out from seed
Parsley - trying to fight the soil problem where it's planted from seed

Any help you can give me would be greatly appreciated.

Thanks,
Janie

If it is French Tarragon, it will not bloom.

Basil- let the flower stalks grow. After a while they will start to turn brown from the bottom of the seed stalk up. You will see small black seeds with four to a pod (where the flower was.) When most of the stalk is dry I cut it off and toss it in a paper sack and let it all dry more. When it is all dry grind it up and blow away the chaff.

Lavender
oregano
thyme
I don't bother with those. Especially the last two because they spread and pieces with roots are easy to pull up and transplant.

cilantro is a no brainer. You will easily identify the seeds. When they are brown and dry then you can take them off the stalk and let them dry a little more. I usually cut them off in small bunches

Parsley will have groups (umbrells, oops, can't spell) of very small flowers. Keep close watch and they will turn into seeds. When they start to dry you can cut off the bunches and set them in a container to finish drying.
Good luck!

Thanks for your help, everyone! : )