"Daarom" is often used to convince people while "dus" is more neutral. - Het regent dus neem ik een paraplu mee. - Zwitserland heeft veel bergen. Daarom wonen er weinig mensen. Om het iets ingewikkelder te maken. Ze kunnen in 1 zin staan. A: Ik voelde mij gisteren niet lekker. B: Dus daarom ging je naar huis.

I usually go for 'dus', whenever that's translatable to 'thus' or 'so' and gives a conclusion to something. While I use 'daarom' whenever it feels like 'that's why' and gives a reason/explains something. You simply need to listen to Dutch more, and you'll start figuring it out.

"Dus" is mainly used as "therefore." You really need to look it up, because you need many sentences as examples. "Dus" can fulfil very strange functions. Think of Descartes: Cogito ergo sum I think, therefore I exist Ik denk dus ik besta.