Other considerations might be:
- Type, leaf v. pellet
- Freshness (how old are the hops and how have they been stored)
- Varietal (lots of considerations here: quality of harvest, alpha %, general flavor notes, etc)
The best advice i've gotten is to keep good records. The more regularly you take notes about various changes in the process the more likely you'll be able to pinpoint where the issue lies. Quality processes (sanitization and cleanliness especially) and quality ingredients will usually get you where you want to go. And that's what I love about homebrewing...it's an equally balanced left/right brain hobby. You can be as type-A and controlling as you want, spending a ton of money in order to control every aspect of the process or you can be as free and liberal as you want, changing things up on a whim. Either way, you've got something to show for your work that hopefully tastes great!
This is so true. My buddy and I both brew. I'm an engineer and approach the process very scientifically with respect to recipes, water treatment, Ph, timing, etc. I also research the hell out of stuff while developing recipes....looking for ideas, "best of breed" recipes, etc. Then I mix and match ideas into my own brew. I also take meticulous notes. I have a form I created that I prep for each brew session with expected values and actual values for things like Ph, volumes, gravities, timing, quantities (in case something changes), etc.
He just gets creative and tries off the wall crap and wings it. He does things on instinct and even changes up ingredients/durations/quantities mid brew based on...instinct? Intuition? Whim? He might jot down the OG (actually, I usually do it because it drives me nuts to not know).
We both brew very tasty beer. The funny part is that, as casual as he is, he is absolutely over the top with sanitizing. On the brew day, he empties his kitchen of every thing, and wipes all surfaces with a bleach solution. It has to be pristine. He won't do all grain because it requires a full boil and he can't do that in his kitchen. I will say it's convenient to have sanitized surfaces to set stuff on.
I brew in my garage. I make sure everything that contacts the wort after it drops below 180 is sanitized, but sometimes I don't even sweep the floor. We sit around in lawn chairs, drink beer and enjoy the process.
We really couldn't have more different approaches to the hobby, but are both brewing tasty stuff.