This is an interesting question. The first consideration is that you probably want to distinguish between what politicians _say_ they stand for and what they actually support. Look at what the politicians from each party actually vote for, and what they actually propose. Don't trust anyone to be honest about themselves - read the proposals yourself, if possible. Remember that a partisan is likely to favor his own side or his own ideas beyond the boundaries of accuracy and honesty, and this especially applies to most news sources in the US today; whenever possible, try to get news reports from outside the US, from sources with as many different political biases as possible. Constantly check their accuracy, so you get a feel for which sources you can trust, but never trust them completely - everybody has biases, and nobody is always free from error. Another consideration is to define your terms - don't simply accept the words people use at face value - remember Inigo's Observation: "You keep using that word - I do not think that word means what you think it means." You might want to define the terms "liberal" and "conservative" for yourself and then see how the people labeled with those terms stack up against them.
Also, use your mind; presumably it's there for a reason. Don't uncritically accept what other people tell you, especially if they have an axe to grind. Try as much as you can to form your own opinions and conclusions rather than let somebody else tell you what to believe and how to think.
That's all hard work, which is why so many people prefer to be somebody else's puppet. Most of us would rather be slaves, since that way we don't have to think for ourselves. Thinking is hard. Making choices is harder than letting somebody else tell us what to do.
So, that being said, what are some good things each particular party stands for? Well, I'm biased - I left the Republican Party when they decided to place their political needs above the country's needs. I have no respect for the present-day GOP; as far as I can tell the entire party has become so ideologically dogmatic that many of them refuse to believe anything that isn't approved by the party. George Orwell would recognize them - he saw it in the old USSR, and wrote about it in 1984 and Animal Farm (among other things), but this sort of lock-step, unthinking ideological blindness doesn't care about 'left' or 'right'; it's just a human thing. We love to be part of a group, and will do anything if the group demands it.
I can't think of any good things that the present GOP stands for. I know plenty of what they say they stand for, but their actions don't match their words. You don't have to believe me - look for yourself.
As for the Democrats, they have little any more that they stand for, good or bad, as far as I can tell. The Republican Party when I was a lot younger is hard to tell from the Democratic Party of today, other than that the Republican Party has always hated the FDR social programs and the LBJ civil rights programs. Nowadays, though, the Democrats seem perfectly willing to go along with the destruction of those programs, too. Few Democrats, any more, seem any more concerned than Republicans with the welfare of the nation. The Republicans are hell-bent on destroying everything that Teddy and Franklin Roosevelt did, and the Democrats seem not to care very much.
As a practicing Christian, I would say that you should look to the teachings of Christ for your insight (ie lean more heavily on the New Testament than the Old), and then decide who you should support based on your conscience. As I recall, Jesus had little patience with those who worshipped power and wealth; with those who loudly and self-righteously preened themselves on how pious they were; with those who spurned the poor and needy, and those who hypocritically said one thing and did another. Whether you wish to use these sorts of considerations on deciding who to support is your call.