[5+ years experience in business development and sales strategy]

The best way to get your first client is, hands down, your own network. Assuming you're launching a consultancy in a domain of your expertise, exploit whatever contacts you already have from a previous endeavour / job.

As for finding your 2nd, 3rd... and 100th client, look into tools used by other consultancies. Depending on the field you're in and who you're selling to (unclear from your post) LinkedIn can be a great tool to identify potential clients and to find out where you can provide the most value.

When it comes down to how to approach clients and maximise the impact of your value proposition, you might find the books by Neil Rackham a valuable read (I would recommend "Major account sales strategy").

Feel free to schedule a call if you want to go more in-depth.