Walt and I plant a lot of garlic every year, just so we can survive between one harvest and the next. Last year's harvest was so disastrous (2/3 of our crop rotted in the ground because of early season flooding) that I had to plant a lot of topsets last fall, just so I could get enough garlic in the ground. This year's crop was fabulous! And some of the topsets I planted last year grew into single bulbs that are so big that I think I may be able to break a garlic head size record next year! (Either that or I will break a record for the most swollen human head.)
We always put lots and lots of worm compost into the bottom of the trench, and mix it in with the soil in the trench before we plant the garlic. And we water our garlic religiously with worm juice. Garlic seems to really love worm compost and worm juice, because, flood-induced rotting aside, our garlic keeps exceedingly well. I've had garlic heads that were still in fine eating shape after being stored in paper bags in our study for TWO YEARS!
Here is a photo that shows the three stages of garlic planting:
1) A this year's top set, which, if planted this fall, will turn into a single bulb to be planted next fall
2) A single bulb that was planted from a single topset bulblet last fall.
3) A garlic head with large, choice cloves. I replant only the largest, juiciest garlic cloves, because they grow into the largest, juiciest garlic heads. Each single garlic clove takes one year to grow into a head of garlic.