The PPC game is much tougher these days but is still one of the best methods to put your offer in front of targeted traffic. Here's some tips if your using Google Adwords.
1. Use one keyword per ad group
2. Write targeted ads
3. Site structure: about us, contact us, private policy, terms and
conditions, site map, and index
4. Test, test, tweak and test
5. Go after long tailed keywords that have a low cost per click
6. Set an affordable daily budget. Rule of thumb is $5 per 50
keywords
7. Maintain at least a 1% click through rate for quality
8. Use Adwords editor to tweak CPC and Ad positions
Yahoo is ranked number 1 last time I checked Alexa.com
I have had great success with Yahoo Marketing Solutions