Pre-Brew Planning

Find a Recipe: The book Brewing Classic Styles has been a good source of recipes so far. I've brewed the Nut-Brown, the Saison, the Stout, the American IPA, the English Barleywine and the Hefeweissen from that book. There are tons of recipes on the web too, but it can be hard to judge their quality if they come from an unknown source or do not have any tasting notes. Magazines like BYO have an online presence - I'm planning to brew a  clone of Alaskan Smoked Porter from that magazine. Finally I've brewed the Stofla from Smoked Beers. I would like to brew a sour / funky recipe from The Mad Fermentationist but as of yet I have neither the patience nor equipment / storage capacity to let a beer sit for a year or more before drinking.

Scale the Recipe: Most homebrew recipes are for 5 gallon batches, but since I brew only 3 gallons at a time I usually have to scale them.

1. Grains & Other Fermentables: I multiply the grain by 3/5 and round to the nearest whole number of ounces, trying to keep the percentage of each fermentable roughly the same.  
2. Efficiency: Some recipes specify a mash efficiency that may be higher or lower than my typical efficiency of around 68%. I aim for my recipe to get the same OG as the original recipe. 
3. Hops: I aim to get the same IBUs as the original recipe, generally multiplying the original hops by 3/5 and using adjusting up or down given the AA% of the hops I have on hand. Again I usually round to the nearest 1/8 ounce of hops.
4. I used to use Hopville.com to plan my recipes but now I use the free software BrewTarget. I try when possible know the exact grain and its producer so that the calculations of gravity and color are as reliable as possible.

Plan the Mash:

1. My normal process is to use a single rest + mash-out. I use the Brewheads Batch Sparge Calculator to calculate the strike, mash-out and sparge water such that I can get 2 runnings of approximately equal volume. This maximizes efficiency.
2. If using a multi-step mash (ie one with more than 1 rest and a mashout) I plan to directly heat the mash in my boil-kettle so that I don't end up with a very dilute mash after all those boiling water additions. Then, I will transfer the mash to the MLT for sparging. In the past, my experience with a dilute mash is that it ends up with a large volume of first runnings and a small volume of second runnings - more like a no-sparge / BIAB method - with attendant low efficiency. 
3. I have yet to do a decoction mash. I may try this for German style beers one day. 

Prepare the Water:

1. I don't have a carbon filter capable of filtering large volumes (though I do have a Brita filter for small volumes), so I use Campden to get rid of chlorine and chloramines. Typically I use 1/4 - 1/2 a tablet for all of the water used in brew day. Usually I let the water sit over night just to make sure the Campden has full effect. (I usually brew in the morning.)
2. Although I have adjusted the water for mineral content and mash pH in the past, I do not understand how to do it properly and have overadjusted an IPA in the past, resulting in a minerally / metallic aftertaste. Apparently, water adjustments should be done only as a final adjustment once a brewer already has other aspects of his or her process down. Since the water around here is moderate adjustments are not necessary, though at some point I'd like to learn how to adjust the water properly.
3. Measure the strike water, the mash-out water and sparge water. Usually I just keep all my water in the bottling bucket, heat the strike water in the kettle, and measure and heat the mash-out and sparge water during the mash.