First, don't attack weak arguments.
In response to David Brooks's column on how to write about politics, Jonathan Chait offers some ideas of his own. It probably won't surprise you that I like Chait's a little better. Here's a pretty good rule:
Don't debate straw men. If you're arguing against an idea, you need to accurately describe the people who hold them. If at all possible, link to them and quote their argument. This is a discipline that forces opinion writers to prove that they're debating an idea somebody actually holds. And quoting the subject forces them to show that somebody influential holds it -- if the best example of the opposing view is a random blog comment, then you're exposing the fact that you're arguing against an idea nobody of any stature shares. This ought to be an easy and universal guideline, but in reality, it's mostly flouted.
You'd be shocked how many professional writers don't do this. Much like a boxer who wants to fight the best in the world, you want to take on the best of your opposition, and their most credible arguments. (My neighbor James Fallows excels at this.)
This is not only for the benefit of people who read you, but for your own. To paraphrase Douglass, a writer is worked on by what she works on. If you spend your time raging at the weakest arguments, or your most hysterical opponents, expect your own intellect to suffer. The intellect is a muscle; it must be exercised. There are cases in which people of great influence say stupid things and thus must be taken on. (See Chait on George Will's disgraceful lying about climate change.) But you should keep your feuds with Michelle Malkin to a minimum.
In the interest of exercising that intellect, I would add something else: Write about something other than current politics. Do not limit yourself to fighting with people who are alive. Fight with some of the intellectual greats. Fight with historians, scientists, and academics. And then after you fight with them, have the decency to admit when they've kicked your ass. Do not use your platform to act like they didn't. Getting your ass kicked is an essential part of growing your intellectual muscle.
To do all of that, you have to actually be curious. You have to not just want to be heard, but want to listen. Brooks makes the point that the detached writer's role should be "more like teaching than activism." I would say that it should be more like learning than teaching. The stuff you put on the page should be the byproduct of all you are taking in -- and that taking in should not end after you get a degree from a selective university. Keep going. You must keep going.