Originally Posted by OrangeJet
It's done over the entire process. For all-grain for instance...mash temperature will affect how malty your beer is (as will the kind of malt you use, of course). During boiling, the amount of hops you use, and for how long you boil will affect bitterness, flavor and aroma. The yeast strain you use, and the temperature you ferment at will also affect flavor.
Many recipes call for hops in the fermentor (dry-hopping) as well. Many, many things affect the flavor...even time itself will affect the flavor.
Do you use whole hops or pellets?
I used whole hops on the beer that I made that came out bad (I even dry-hopped with them). Is there anything that you have to do to them before using them?
Even though I doubt that's what ruined the brew, I've stayed away from them since.