Follow your nose
When I come back from Europe, I invariably have a string of garlic in my luggage. Yes, the smell gets into my clothes regardless of how I pack it (usually wrapped in newspaper and aluminium foil, then secured in a plastic bag and sealed with duct tape), but that doesn't stop me.
If you think all garlic tastes the same, you're wrong. Just as there are many varieties of grapes, the taste of which depends on where they're grown, garlic differs from place to place, too.
I came back from a trip last month with purple-hued garlic from France and off-white garlic from Italy. Although a few heads of Italian garlic have been mixed into the kitchen basket that holds onions, shallots and Chinese garlic (which looks similar), I can tell which type it is by how it feels: the stuff from Italy is firmer and heavier, it's harder to crush with the side of a cleaver, and the papery skin is difficult to peel off.
When I cook with garlic, I tend to slice each clove in half to remove the green sprout inside, but the Italian garlic is so fresh (it's this year's crop) I haven't had to do that.
When buying garlic - wherever it's from - feel the heads for firmness and reject any that have started to soften or smell bad. Garlic is also available in jars as whole, peeled cloves, or chopped. While I might use the former in a pinch, I'd never buy the latter because I dislike its metallic taste.
Raw garlic has been linked to botulism, carried by spores that thrive in an anaerobic environment. Garlic oil was popular until people realised that leaving the cloves covered in oil created the perfect climate for nurturing botulism. It's easy enough to make fresh batches of garlic oil as you need it: cover finely chopped garlic with oil and you can have a batch within 15 minutes. If any is left over, strain off and discard the solids, store in the fridge and use soon.
Even better - and safer, because botulism spores are killed by cooking - is fried garlic oil. Thinly slice some garlic and put it in a small pan with enough oil to cover it. Cook over a medium-low flame until the oil sizzles. Lower the heat and stir frequently until the garlic is a pale gold, then leave to cool. Strain out the garlic 'chips' (they're delicious scattered over steak or fried noodles). The garlic oil can be drizzled over soup noodles or used in stir-fries.