Lie well and lie often, then accuse you opponent of lying.That's the recommended approach- it works! it makes you look "aggressive" and "dynamic."
One example was when Obama explained the fuzzy math of Romney's budget plans, and Mitt responded with indignation, insisting that his plans will balance the budget by virtue of bringing in MORE revenue by reducing the tax rates of rich people. The Congressional Research Service and most economists reject that, noting it has been tried many times and has never achieved the desired goal. In 2012, the concept is especially silly. Tax rates for the rich are already low- Mitt's tax rate is lower than mine- so you run into diminishing returns. What next, zero taxes for the rich and we will suddenly run a budget surplus?
But Mitt did speak with passion. It seemed as if he might actually believe it.