To ensure that your PPC campaigns are receiving full conversion credit in Google Analytics, be sure to tag your destination URLS with the code: utm_nooverride=1
This tag will prevent a return visitor's conversion from being attributed to "direct" if, after originally visiting from a paid ad, they return directly or from another source. Proper tagging will also help synch conversion tracking between AdWords and Analytics reports.
If you're currently using Google's auto-tagging feature and your current destination URL is http://www.mysite.com, the new URL should read http://www.mysite.com?utm_nooverride=1
Manual utm tags can follow the nooverride tag.