How does one figure out if a think tank is liberal, conservative or independent?

I really don’t know, but I would perform a test. Put a crying baby in the room and you could probably figure it out.
The liberal will give it toys (when its probably wet, hungry or sleepy)
The conservatives will say its not our problem, lets go to lunch.
The independents will look at each other to see who does what first so they can say it was wrong.

One reads a few reports or publications, and then sees if they lean to one philosophy or another, or if they seem to be objective.

Just listen to them. It will be obvious.

If you look at their website, in the section where they talk about their mission or history it is usually stated pretty explicitly what party they are funded by.

It depends on what you mean by “independent”. Do you mean, not committed to any specific political party? Do you mean, moderate – and if so, moderate for the sake of moderacy, or moderate because they genuinely fit there? How people use “independent” varies rather greatly.

Just look at their policy recommendations. It’s easy to tell from that. As far as I know, they are not usually funded by parties. They generally raise funds directly from supporters. Some apply for and receive government grants. For others, you have to look at their client lists. At the think tank I used to work for, our clients included unions, various government entities, a medical society, several different foundations that were interested in a wide variety of issues from health care to immigration reform. Our mission statement included the word “progressive,” I believe.

@zenvelo & @wundayatta have it exactly right. As Matthew 7:16 tells us, “Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles? 17 Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.”

One thing you definitely can never trust is their name. The Think Tanks aimed at building oligarchy or at pushing a particular industry or group’s interest at the expense of all else always resort to Newspeak when selecting a name. Likewise, the titles of the papers they release will be equally deceptive.

It’s simple. If they claim they’re liberal, they’re conservative. If they claim they’re conservative, they’re liberal (their economic rhetoric is anyway) or fascist. If they claim they’re independent, they’re fuckin’ liars. In the U.S., “independent” is a buzz word for Republikan voters who say they don’t always vote Republikan. John McCain can be independent, but Dennis Kucinich can’t.

As others have said above me, judge them by their fruit. When you watch or read their material enough it kind of throws the answer at you, just like a biased news source.