Probably the most important thing you can do to improve your final beer quality, besides basic sanitation, is controlling fermentation temperature.
There are a few reasons you may need to do this.
Maybe you want to brew both Ales and Lagers. They have very different temperature requirements. Most folks stick with brewing ales for quite some time due to the difficulty in precisely controlling lager fermentation.
Or you may live somewhere that gets too warm or too cold to maintain a stable ambient temperature. Sudden changes in temperature, especially during the first few days of fermentation, can really change a beer.
Yeast is a living organism and how well it ferments the beer (or wine) can be impacted by temperature. Too cool and it may stall out and not fully ferment the wort. Too hot, and it may produce higher alcohols and other off-flavors that make the final beer unpleasant to drink.
We'll go over a few important steps to get your fermentation temperature under control.