How do you save your seeds for planting the next year?

How do you save your seeds for planting the next year?

This will be my third year gardening. My gardening plans and experience: Year one- I planted a few rose bushes in the front yard. Year two- I planted a few baby rose bushes in front of the big rose bushes. (all roses still doing well) I also rented a tiller for the back yard veggie garden. I planted about 15 different seeds. I grew tomatoes. The other plants that grew were mistaken for weeds and I riped them from the ground. Most just didn't grow. This year: I actually wrote out/drew out a layout of the garden. I read the backs of all the seed packets. I'm reading 'The 20-minute gardener'. My husband made me a small (about 2x3 foot) green house so I can start my seeds indoors. My garden space is roughly 13x8 feet. I am determined that this year my garden will grow!!! I am planting: sunflowers, corn, onions, pumpkin, squash, watermelon, cucumber, carrots, broccoli, bell pepper, peas, big tomatoes, cherry tomatoes, hot peppers, sage, oregano, cat nip, chamomile, lavender...and whatever other seeds I get my hands on. My veggie experience is practically nil. Just last years tomatoes. I'm sure I'll have many questions as the season progresses. As for now I do have a few questions already. My garden is fenced on all four sides...will cats still try to steal my cat nip? How can I keep them out? Do lavender plants have a strong smell? Is there a flower you can reccomend that has a nice, but not over powering smell? Do you advise using the black plastic ground cover in a veggie garden? How do you save your seeds for planting the next year? Thanks!
Me too!

Me too!

Happy Beltane!

Happy Beltane!

Blue flowers

Blue flowers

my wall of rosemary

my wall of rosemary

My small space

My small space

Questions and a plant ID

Questions and a plant ID