I have been voting for decades, and I am not getting any better at it. The candidates can conceal who they are far better than I can learn who they are.
The news media rarely helps. At best, it covers what candidates say. A vote based on campaign coverage is like buying a car based on media accounts of what car manufacturers are advertising. In politics, there are no Consumer Reports.
I have some rules to limit my ignorance. First, ignore political advertising, especially anything I'm inclined to agree with. It is incomplete and deceptive, at best.
Second, vote for no one who claims not to be a politician. If you're running for office, you're a politician. And if you claim not to be, you're like a doctor promising not to practice medicine.
Third, simply being an incumbent makes you neither effective nor stale, and being a challenger makes you neither refreshing nor unprepared. What counts is what you have actually done. But how to find out? I respect politicians, but they are masters of deception. Trying to learn what they have done is like investigating a crime scene without forensics. Motives are even harder to discern. Some say Gavin Newsom showed great courage in permitting gay marriage in San Francisco in 2004, others that it was crass opportunism to ensure his re-election the next year. Who knows?