Many marketers like to use Google's free keyword tool for keyword research.
Using this tool, you can see the estimated search volume for a keyword phrase over the period of one month.
New marketers sometimes make the mistake of targeting keywords that are too competitive.
For example, they pick keywords like "make money" or "credit cards".
If you are just starting out, you have like zero chance of getting ranked in the first page of the search engines for those keywords.
However, you can start by targeting keywords that are easier to rank, but with less traffic.
Some people call them "long tail keywords".
Long tail keywords are phrases with three or more words in them.
So instead of targeting "credit cards" directly, you can try to target keywords like "credit card quotation" or "credit card application", etc.
You can use the Google keyword tool to suggest a whole list of keywords for you.
Pick the ones with at least 1000 searches per month.
However, note that this is just an estimate.
Traffic levels often change as the trend changes.
So you may experience different levels of traffic when you target those keywords.
Nevertheless, having some estimates to guide us is still better than shooting in the dark.
These figures can be an indication of how active a market (or niche) is.
Over time, as more and more of your articles are ranked in the search engines, you may then start to target the primary keyword phrase "credit cards".
This is the overall SEO strategy that marketers should adopt.