I'm not going to pretend that everyone will like miso soup, because if you're Western, these ingredients are going to be pretty alien to you! Dried, fermented smoked tuna, seaweed, fermented soy beans, and that 'tofu stuff'? What is that all about? OK, there's spring onion in there, you'll know that one, but the rest... well, keep an open mind, because you might just decide it's rather delicious. So don't let that put you off! (And you can always make my dashi stock substitute as a base, which doesn't contain fermented tuna or seaweed - and the vegetarian version of dashi stock has dried shiitake mushrooms in it).
It's also incredibly healthy. Miso (paste) is a bit like the mythical 'apple a day'. It's very good for you. And very tasty too - if I say it's a bit like marmite, it's not because you'll necessarily love it or hate it, but it's full on umami flavour which gives a real depth to dishes. There are various different coloured miso pastes - the lighter, the milder and sweeter; the darker the more savoury and stronger. With miso soup, it's somewhat down to personal taste. I'd recommend a medium/red miso paste. Something between the colour of a cheap milk chocolate, and David Dickinson's mahogany tan (red miso). If you're trying to avoid gluten or soy, there's a little information here which might help you in what you select to cook with, and/or Clearspring make organic (white) miso which is gluten free - see here.
So here's my basic miso soup recipe (with tofu and wakame in it). I also like to add mushrooms to this, in fact, you can add in any vegetables. If you don't fancy wakame (give it a go first, it's amazing stuff! Plus it's amazing in this Wakame and Shaved Vegetable Salad in a Soy-Ginger Dressing with Toasted Seeds, too!) then wilt some spinach into it, instead. Oh, and if you like your spice, shake some 'Shichimi Togarashi' over the top, a Japanese spicy seasoning containing chilli and sesame seeds amongst other things. But beware, it likes to lurk at the bottom of your soup, waiting to burn your throat on the last mouthful!
150g tofu, drained weight, cut into 1cm / ½ each cubes (silken/medium – the most common variety found in the refrigerated section, in large white blocks in water, e.g. Cauldron original tofu) 
400ml dashi stock* (see the highlighted dashi stock blog for recipe or substitute, and gluten free information) [4, if home-made]
5g dried wakame seaweed 
2tbsp light (or medium/red if you prefer) miso paste (for gluten free, only certain brands, e.g. Clearspring white miso - check labelling) 
1 spring onion, sliced finely 
Soak the wakame seaweed in cold water for 5 minutes. Meanwhile, bring the stock to the boil (or add boiling water to the miso soup sachets). If you are planning to add any extra vegetables (e.g. mushrooms, daikon, carrots etc.) add them at this point and poach until just tender.
Add the wakame seaweed and simmer for 1-2 minutes. Add the tofu and heat through for another minute or two until heated through, and then take the pan off the heat. Take a ladleful of the hot liquid, and add to the miso paste in a small bowl and stir/whisk in until incorporated and then add the loosened miso paste back to the rest of the pan, stir in, then serve garnished with the sliced spring onion. Don't boil the miso, if you can help it, or you'll lose some of the health benefits.
*or if you haven’t got dashi stock, use 2 sachets of miso soup (e.g. Yukatame brand which is gluten and MSG free [18 calories per sachet], plus 1 tsp light miso only [4 calories]). You can also buy instant Dashi stock (or you could use instant bonito stock), but check that you are happy with the ingredients, as some contain MSG which some people prefer not to consume.
Add extra vegetables to bulk out the soup, such as mushrooms (I like adding mushrooms, and they’re only 16 calories per 100g), sliced daikon, sliced carrots, spinach, or even potatoes. Simmer them until tender before adding the wakame.