I'm relatively new to this as well. Only put down about 4 so far but am becoming quickly obsessed.
Keep in mind I am by no means an expert so I may be wrong with some of the below.
What I have read is that the most important things for homebrewing are
- Cleaning/sanitisation
- Temperature control
- Everything else (lol)
Cleaning and sanitising for the risk of infection, the temperature control effects how your yeast behaves, two high (above 30) and it dies (every yeast is different so may vary from strain to strain) too low and it goes dormant and does not effectively convert the sugars into alcohol.
Each yeast has a ideal temp range (roughly 18-22 for ale yeast but this varies and larger yeast is completely different) when you get too high above this it can produces fussel alcohols (different to ethanol and has a different flavour and can cause headaches) and also different byproducts like fruity esters in larger quantities. This is not necessarily bad in some amounts (Coopers pale ale has pear esters as a signature flavour) but in large amount is generally undesirable (extra buttery flavour I had in one brew was not great)
I think the main thing is having consistency in temperature as this will not stress the yeast (even if it is at 24 if it stays there the yeast is happier than if it changes a lot)
Also what the conditioning phase does (outside the initial 5 or so days where it is fermenting vigorously) is it cleans up and eats a lot of the byproducts it made in the first phase, if this was done at too high a temp there is too much for the yeast to eat/clean up and you are left with too much of these in your final bottled product. Bottle conditioning again mellows it all out but can only do so much.
I have no temp control at the moment so am just keeping in a relatively stable temp cupboard in my house and wrapping a wet tea towel around on the hotter parts of the day and putting a fan on it to remove heat and wrapping in a blanket or something to insulate on cold nights, not ideal but has helped regulate the temp somewhat. Next investment will be to solve this issue.
I would recommend reading How to brew by John Palmer (free online version) It helped a lot with learning how it all works. Keep in mind he talks more about using un-hopped extract but the yeast and temp stuff is the same for kits.
http://www.howtobrew.com/
The other thing I have done to elevate my brews was do a partial mash. I just followed the guide here (linked below) but did more of a boil and added more hops. Last time I also steeped some crystal grain which is another step/layer of flavour again.
https://aussiehomebrewer.com/threads/pimping-a-coopers-kit-with-a-partial-mash.72607/
Hope this isn't to rambly and some of it helps.
