What are some hacks and basics for improving and enhancing a song recording in Audacity?

Answer 1

The bread and butter of any sort of music production is going to be using EQ and Compression respectively. Making sure you have a good handle on EQing out annoying frequencies and making sure different elements of the recording fit well together in the mix (have their own space in the frequency spectrum).

Compression evens out dynamics/glues parts together so that a vocal or a guitar part sits better within the mix.

Although a full tutorial of EQ and compression isn't within the scope of this answer, there are a ton of great resources online walking through the basics of each.

Aside from that, general level balancing (making sure the volume of each part works) is a great quick trick to get a mix sounding better. Making sure the most important elements of a song are the loudest and ordering the levels by order of importance is a great way to get something sounding better right away.

Hope that helps!