I think respect is a major factor. Corny, yes, but there you go.
Be respectfull to others, be respectfull in your posts. Over time, as people get to know you, you'll see a return on it; people will take you more seriously, what you say carries some more "weight".
Time itself is also a factor I think; over time people get to know you, or at least become familiar with your "name". As long as you haven't been acting like a jackass the whole time, your reputation as a "good poster" should grow.
For example, don't refer to commenters to some article on some obscure forum you linked to as "fanboys", like I recently did.
You can voice a strong opinion every now and then and "lose some points", just make sure the balance stays positive.