For what its worth here's my twopennyworth. The preparation, storage, and cooking of Garlic is quite a large subject on its own, and I was thinking of putting it in the hints, tips etc topic. It is a well known fact that Garlic does not freeze very well, the process releases all the bitter acid as it defrosts, so if you have to freeze it, they do so in small portions and add it frozen to the dish you are cooking, don't let it defrost. Being a business I have access to the wholesale outlets, so I buy Schwartz catering jars of pureed garlic (as most chefs do). It is not as good as fresh Garlic (its has a gassy smell and slightly acidic taste from the preservatives), but it suffices for bulk cooking.
Ginger freezes well, but you should never peel it when you use it fresh or frozen. Just wash it well and remove any dodgy bits. All the flavour of Ginger is concentrated just under the skin. Again you should add frozen Ginger straight from the freezer, don't thaw.
If you grate I recommend a Microplane, which will shave rather than rasp the Ginger; better still use a mini-blender.
Similarly, you can freeze Coriander quite well. Just wash well, remove the leaves and discard the stems, dry it very well, and freeze it. Don't thaw you must add it completely frozen.
Happy cooking
C P