You don't have the ability to interpret the information you don't have.

I will give you both.

When discussing a topic it's important to have some information on it. More important still is the ability to interpret and produce similar data.

In a recent debate on climate change a friend challenged me that they could cite many articles that referenced figures in comparison to the two that I gave them. The difference between the articles was clear to me and I challenged her on this. It seems that it was not clear to her.
The two articles I supplied were both of a scientific nature; the first described a simple experiment and somewhat more complicated math to demonstrate that carbon emissions lead to global warming. The second was a scholarly article including its data set. She supplied, in return, three opinion page articles from popular online news sources, one of which had an image of a chart in it.
I could spend some time debunking each of the claims in each of these articles but my experience suggests that this just leads to dropping those articles and not the ideas. (also great debunking is likely already on offer, links?)

My focus instead should be supplying the tools to analyze the information in these articles and an explanation of how to find the full data sets. If this sounds more like an introduction to the scientific method than a conversation about climate change that is because it is. The title suggests, rather rudely, that my opponent does not posses the
Requisite skills to discuss this topic; these are general skills that will be useful in dealing with any information that you wish to present or that has been presented to you.
There are some basic things that you need to start. Since discussions of this kind often involve charts I will start there.
Charts are tools to make data easier to interpret they are a form of info-graphic. The important things to know about graphics is the scale and data set used.
What is important is a continuous representation that Enhances the intuition of the situation. If the chart is misleading or obfuscates the information than it can give a bad intuition. Additionally if it extrapolates too much from too little information then it may mislead due to graininess.

It's relevant to mention Nyquist Theorem here. The essential part is that you need to take samples at least twice as often as the period of the thing sampled. Imagine a sine wave that you sample at the same period as the wave. You will end up with a line.
If you over extrapolate from this limited information you may end up drawing the wrong conclusions.
There are also various ways to graph information. Depending on what you are comparing and how much data you have you will want to pick a specific type. Bar graphs are useful for comparing relative points and do well with limited data. Pie charts should only be used when representing the percentage of something when all the numbers are known (if you are projecting say so). Line graphs are very useful when you have enough information to not smear out the important trends.

The next key to making informed choices is understanding information sources. How do you separate good information from bad? How do you know when you have enough data to successfully model a given instance? There are a few strategies that we can employ. The first simply being if we trust the source ( this of course can lead to lots of creeping errors if we trust the wrong source so let's put a low information value on this). The second being the availability of said information ( how difficult is it to check for yourself? How many independent sources can provide this?) troubles arrive in this verification process and you may be in a situation where there is only one source of good information. But in a free and open society you should have multiple places to view the same basic information from. If the information is experimental are you viewing the whole result or just part, can you recreate the experiment? If you have multiple confirmations from independent sources and you are unable to reproduce the result (historical results for instance) then you must weight the value of your sources and the story they are giving you. We should use the idea of attempting to fit to the simplest explanation for the information at hand. If his contradicts something known we should seek more information on both the new idea and the known one. If only one can be true we should take the one which is better supported. The principle of simplicity and elegance in explanation is called Occum's Razor. This is he assumption that given otherwise equal evidence the description with less "moving parts" is the least likely to break down. This can be seen in reasoning the premises from the conclusion ( my practice of determining what is required to be true for a given belief, the domain of necessary truths given a certain set of premises).