In doing some research I found in a few places that it is better to not use commas when entering in your keywords and go off of just a few like 5 or 6 keywords. Which is best? Which worked better for you?
Sites with comma or no comma in keywords showed up well in serps. It may not be a major factor to be concerned about.
Commas separated in keywords will not help search engines treat them as separated. For search engines, comma and space has the same function, and using comma is just for human being's confortability.
Using commas or no commas between keywords is simply a personal preference. Using no commas at all in this tag is basically the same thing, since most engines appear to treat commas as a space.
It's really a personal preference. But, I prefer to remove the commas because it really could lead to more keywords or more 'combinations' of keywords. For example, look at these two: big widgets, red widgets vs. big red widgets With the first example you get two keyword phrases. But, with the second one, it could mean more: big, red, widgets, big red, red widgets, big red widgets. You actually have more keywords with the first one but can get more out of the second one (so I go with the second one).
I think there's absolutely no difference between using a comma or just leaving a space. I'm pretty sure search engines are smart enough to not make a comma very important
If you mean meta keywords = yes you should put only important keywords not more than 6 and those keywords should be contained in page content. Use it smart and it won't hurt you but meta keywords will not use for ranking your site, just for adsense bot to crawl and place relevant ads on your site but spammy is mean no good.