My Korean friends tell me that only their grandmothers make their own kimchi. I'm neither Korean, nor a grandmother, but I love to make kimchi. It's delicious with many dishes, not just Korean food. I like it with everything from steak, sausages and roast chicken to instant noodles and sandwiches.
There are no hard-and-fast rule about the seasonings: some cooks (including me) add seafood, you can vary the amount of gochugaru (Korean chilli flakes) to suit your spice tolerance, and some versions don't use any chilli. I like to add a lot of other vegetables to my cabbage kimchi, but they are optional. The most critical step is the salting of the cabbage: if you don't add enough salt, or if you don't allow enough time for the salt to soften the cabbage leaves, you could end up with a mouldy mess.
I make cabbage kimchi in small batches, so I can eat it before it becomes over-fermented. The amount of kimchi paste in this recipe is enough for about 1 1/2 large heads of cabbage, but I use only half a cabbage at a time. I store the remaining paste in the fridge, so it's ready for when I want to make more. If you're cooking for a large number of people, triple the amount of cabbage (and other optional ingredients), and use up all the paste in one batch.
When buying cabbage, look for large, fat heads, rather than long skinny ones (and the same goes for the white radish). Don't cut the cabbage from stem to tip, or else you'll end up with lots of small bits of leaves. Instead, cut the cabbage through the stem end, then tear it in half. Tearing the cabbage lets the leaves divide along their natural lines so the pieces are larger.
In Hong Kong, the best place to buy the ingredients is the Korean shops along Kimberley Street in Tsim Sha Tsui. For the gochugaru, buy finely ground chilli flakes, not the coarse ones.