The "right keyword" depends on different factors.
First, it has to speak to the search intent that you want to market to.
For example, if you are selling widgets and you want to drive search traffic to a page that sells widgets directly, the keywords that you're targeting must have a "high buyer urgency."
So buy widgets, best widgets, pop widgets, are your most natural keyword targets.
But believe it or not, if you are looking to sell widgets, it may make a lot of sense for you to also target keywords that are informational in nature.
The reason why you might want to do this is because a lot of the commercial or "direct keywords" that you would naturally want to target are very competitive and in many cases saturated.
The better approach would be to get your foot in the door so to speak, by targeting informational searches related to your target keywords.
For example, if you're selling widgets, maybe you should target keywords and topics like "How do widgets work?", "How to repair widgets?", "How do you know it's time to replace this widget?"
Do you understand where I'm coming from?
Because at the end of the day you're getting your content in front of the same eyeballs that will eventually buy from you once they get some of their initial questions answered.
At the very least when you target informational keywords, you can build trust.
Also you can get people to sign up for your mailing list by offering them freebies like booklets or checklists.
Once they are on your mailing list, you can then start directing them to more of your pages that have a commercial intent.