I've been doing marketing for a while. Mostly for my own businesses. After some painful trial and error I found out that direct marketing is usually the more effective choice for a lot of businesses (including startups).
Adwords might seem direct, but its not. It is marketing at large, and depends heavily on things that are out of our control. Software like ad-blocker makes things worse.
Yet, the do work as a combination with direct marketing. Approach them as you would a radio ad on a small station.
Now, cold calling. There is nothing like selling over the phone. It just works, and repeatedly.
I will always try to work into any campaign some kind of calling program. It allows you to break the ice. People do respond well to it and response ussually raises significantly.
Problem with cold calling and phone marketing is that people approach it wrong. They let the prospect take control of the conversation. They call with just some script and maybe behind a computer.
I don't. I prepare as if going to battle. Everything I might need is close and ready. Pen, notepad, calculator, specs sheet, the actual product, at least 2 scripts, the computer connected to the net with DDG ready to go, etc.
I take command of the call and just set out to conquer. Now, I hardly ever sell a product on the phone anymore, but I sell the appointment which will ussually lead to the sale.