There has been a brief (and very pleasant) few days of dry weather here in North Lincolnshire - a perfect opportunity to plant garlic! Yes, you can plant garlic in early spring, but the results can be a bit disappointing. It really needs a bit of cold weather to inspire it to produce fat, heavy bulbs.
You're best off buying your garlic for planting from a garden centre or an online supplier (I can't recommend The Garlic Farm enough! A good range of huge bulbs in excellent condition that are trouble free to grow) rather than stuff from the supermarket. Or you can scrounge some from anyone you know who grows their own*.
Garlic is fairly undemanding, though they do best in well drained, fertile soil. Last year MikeyFox treated me to the Garlic Farm's Garlic Lovers Seed Collection (9 varieties of garlic - on nom nom!), which were planted out in our raised beds. Whatever wasn't scarfed down green in June I harvested at the end of July & stored. So I'm using the most successful varieties of these stored bulbs for seed. Garlic is asexual (meaning it doesn't need pollinating, not that it's indifferent to rumpy-pumpy), so each clove will grow into a clone of the parent plant (and you don't have to fret about cross-pollination). There is something mildly disheartening about harvesting a large, perfectly formed head of garlic & instantly thinking 'I can't eat it', but on the plus side, saving your own seed encourages biodiversity, avoids the juggernaut of F1 hybrids & monocultures & allows you to dabble in a less crazy-haired form of mad science (like seed selecting & plant breeding). Also, it'll save you a few quid!
This year I'm planting Chesnok Wight (hardneck), Albigensian Wight (softneck), Lautrec Wight (hardneck), Iberian Wight (softneck) & Elephant garlic (I like to try & have an equal balance of hardneck & softneck varieties of garlic. Softnecks store better, but hardnecks produce a flowering spike called a 'scape', that you can chop off & use in stir fries, pesto & lots of other delicious, summery dishes).
Before planting, break the bulbs (carefully) into individual cloves. Any that are damaged or bruised are best used in cooking, as they'll rot or succumb to infection (which would be a terrible end, when they could end up being eaten instead!). The cloves are planted 15cm (6") apart in rows 45cm (18") apart (actually, they're planted further apart than that, so in spring I can sow carrots between the rows of garlic & onion to deter the dreaded carrot root fly). The smaller cloves from the middle of the bulb can also be planted out, but you can put them a little closer, about 10cm (4") apart (though a smaller clove will give you a smaller bulb. A big, delicious clove will give you, with luck & good weather, a big, delicious bulb).
I'm also planting Elephant garlic, which is actually a leek, rather than a garlic. It's rather aptly named! It also has a milder flavour that people who usually balk at raw garlic find a lot easier to handle.
They are best off planted September - October, about 30cm apart (they are big, after all). You can plant them later, but the closer you get to spring, the more likely it is that the bulb will not separate into cloves, and you'll pull up one solid bulb of garlic. A nice idea, but in practice it's a little intimidating. The bulb will also have little hard shelled bulblets (they're actually corms) clinging to the outside. These can be planted out right away, and will produce a small round - a solid ball that hasn't divided into cloves. Leave them another year & you'll get a full sized Elephant garlic. Woo!
*So that's a sentence that won't get me into trouble...