I've got my trusty google calendar to refer to, as well as my gardening journal. In the gardening journal I keep notes of what seeds I'm buying, what brand, cost, what date they're to be planted, the actual date they're planted, and any sort of notes from what I've learned by reading articles or notes from actual experience growing the veggie in previous years. If I've got extra seeds left over, I seal the package up real tight and toss it into the container with other leftovers. I might even reuse them later in the year for a fall garden. We'll see! Then I put the container in a closet and out of the way until its time to plant again!
So far I've got everything running smoothly. We'll see what happens when I've got an entire greenhouse going in this room! Hopefully with the way I've got things planned out, I will just be cycling out different trays of seedlings. When its time to transplant, it will also be time to start another seed. We'll see! How do you keep your garden organized?