Cold Outreach: How to Maximize Meeting Rate

I've been searching for 6+ months and trying all sorts of things with my cold outreach campaigns to maximize my meeting rate.

Some of the things I've experimented with are personalizing emails, email subject lines, email structure, including meeting links in emails, email content, LinkedIn messages, cold calling, and the sequence of outreach steps, among other things.

There has been some improvement over time, but not enough. I'm generating 8 to 10 meetings for every 100 leads.

Do you have any tips to improve the meeting rate?