How do you capture client requests?

I presume that some of us here provide bespoke services (i.e., freelancers, design/dev agencies, etc).

How do you capture and track requests from your clients? Do you require that everyone submits their inquiries via a form, or directly to Trello/Asana/Jira? Or do you work via Slack?

Thanks in advance. I've been working directly via Slack, and it's sometimes quite overwhelming.