You'll need to get a testing platform, like Google Website Optimizer and run a simple split A/B test. Since your site is struggling with low traffic, avoid multivariate testing, as the time it would take to generate enough traffic to gauge the success of multiple combinations of on-page factors could be too prohibitive.
Don't make any judgments until the test is finished and you have statistically significant results. Basing your choice of one headline or call to action on incomplete data is a surefire way to waste your time and delay success. Meanwhile, supplement your test by driving traffic through PPC buys.