OK, now I'm back in front of my computer, have some links.

Home brewing recipe calculator

BJCP 2008 Style Guidelines

Keep in mind, there was a recent update this year, but I can't find a resource that is as easily accessible as the 2008 version yet.

Beer recipe design basics

Keep special attention to what was said on grains. 80% pale malts, 15% caramel malts and 5% chocolate malts. The percentages are in reference to the entire grain bill, and can be flexible.

For example; the BJCP guidelines state that for an ESB,

Pale ale, amber, and/or crystal malts, may use a touch of black malt for color adjustment

may be used, so naturally the pale malts = 80%, total amber/crystal malts used must account for the rest, and if black malts are to be used, no more than 5%. May use sugar adjuncts, corn or wheat.

So, the grain bill for a 1 gallon ESB recipe would look something similar to below...

Malts:

• 1.6 lbs UK Maris Otter Pale (80% of total bill)

• .2 lb UK Crystal 60L (10% of bill

• .1 lb UK Amber (5% of bill, + crystal % = 15% of bill for all caramel type malts)

• .1 lb Torrified Wheat (5% of bill, small amount of adjuncts are typical, but again, refer to style requirements)

2 lbs total

For hops, I use both the descriptions from BYO and the descriptions presented by the manufacturer to make my decisions, as well as taking into account what fits the beer "style." Just remember that the descriptions are vary subjective, and vary wildly. The best way to be know what hops to use for what would be through hands-on experiences. That being said, Alpha Acids are a great indicator for use; the higher the amount, the more bitter your beer will be, especially if used at the 60 minute mark. If you want a softer bitter, use hops with less AA.

For example Saaz (typically described as a hop used for aroma purposes) can be used for bittering purposes (eg: introduced into the boil at the 60 min mark) if you don't wish for an excessively hoppy beer, as it's AA is measured around 3-5%. In fact, that's what I did on a recent Hefeweizen recipe, and it turned out great. It's all dependent upon what you want to do.