Accurate valuations

Hi all,

Looking to purchase my first home with my partner. She already owns her house and we are looking at selling it (brisbane) to help us upgrade to a forever home.

I’m new to all this and a lot of the houses are falling in our search bracket (1.3-1.8) but don’t list a clear value.

What are the hidden secrets to understand a rough price guide on a house without contacting the agent?