Hi,
First of all do a small research on the agency's portfolio as per your tech requirements like if you are looking for Blockchain application you should check related work done by them in that niche as Dapps, NFT marketplace development , cryptowallets etc.

Secondly , check their online presence on social media platforms preferably- LinkedIn.

You can connect with me if you are looking for mobileapp development, website development, blockchain services.

Thanks
Saurabh A.