How do you design a recipe?

[jaroporter]

also, i think it's important to not get stuck in the mindset that recipe designing is all about fine increments of malts and hops. yeast choice and fermentation practises are just as - from experience i'd be tempted to say MORE - important. loads of recipes go into massive detail on malts and hops but don't mention yeast which seems crazy when so many diverse english pale ales are brewed from almost exactly the same grainbill and similar hop schedules.. actually i'm gonna draw this back relevant - two chefs can come up with totally different dinners from the same recipe. as has been said, pay attention to processes and learn from experiences. if in doubt about a hop combo - a mini trial batch is always fun!
seriously though, i've never had a beer turn out undrinkable due to the malt or hop recipe. but i've chucked a couple where i've neglected the yeast..

[Capn Ahab]

also, i think it's important to not get stuck in the mindset that recipe designing is all about fine increments of malts and hops. yeast choice and fermentation practises are just as - from experience i'd be tempted to say MORE - important. loads of recipes go into massive detail on malts and hops but don't mention yeast which seems crazy when so many diverse english pale ales are brewed from almost exactly the same grainbill and similar hop schedules.. actually i'm gonna draw this back relevant - two chefs can come up with totally different dinners from the same recipe. as has been said, pay attention to processes and learn from experiences. if in doubt about a hop combo - a mini trial batch is always fun!
seriously though, i've never had a beer turn out undrinkable due to the malt or hop recipe. but i've chucked a couple where i've neglected the yeast..

This. This. And this again. Malt and hops affect the balance of a beer, but poor fermentation is generally what makes it undrinkable. Pitch the right (healthy) yeast, at the right temp and in the right quantity and you have half the battle won.

In terms of malt and hops, most homebrewers chuck the kitchen sink at beers when they start brewing, and over time come to realise that simplicity is best. A good basic grist (that can be adjusted to any gravity) for a bitter would look like this:
Pale malt
5-8% crystal
0-5% wheat/oats/flaked barley
0-2% choc/black/roast barley

Use English hops to a bu/gu ratio of around 0.6-0.7 and split the early and late additions 50% at 60 mins, 25% at 10 mins and 25% at 0 mins.

Above all use a good English style ale yeast with some character (Mauribrew 514 is great) and make sure it's conditions are favourable and you won't go far wrong.

[jaroporter]

to be clearer about the yeast also, my standard bitter recipe is basically what Ahab described above. i've fermented it with quite a few different dried and liquid yeasts and some come out fruity and light, while other yeasts really emphasise that fraction of dark malt and make it like drinking a dark ale. i reckon it's really worth splitting batches of a basic recipe with different yeasts to find out the effect they have on the beer, then consider that when coming up with the grainbill

[Barley Water]

You are correct. This hobby is all about fermentation control. Want to see what happens when you fool around with the fermentation paramenters start brewing either heffeweizens or Belgians. Fluctuations in temperature, gravity, pitch rate etc. will be very easy to taste in those styles. After you get schooled using WLP300 for instance the knowlege gained will make all your beers better, including lagers.