I get best results at:

1 forums
2 manual traffic exchanges
3 free ad boards (however you need an eye-catching one-liner ;-)
4 paid popup advertising, but that can be a costly business

What is not working for me:
safelists and PTR

But I am still searching for the most effective way, so if you have a good suggestion, please let me know ;-)

I think it depends on your product or service too, what is the best channel to use.

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