Then you'll need to go off the data you have. The keyword planner is still a good tool to use, it just can't be 100% trusted. You can also play with the Google auto-suggest (waterfall) that pops up as you type things in. The suggestions are based on search volume.

There are also keyword research tools out there that can help. SEMRush, SpyFu, etc.

Also look at competitor sites that already sell the product. See what they are targeting in their title tags and H1s.

It's important to look at webmaster and analytics data for this. The keyword planner isn't exactly accurate. I see traffic coming from keywords all the time that don't have a search volume in keyword planner, or have a vastly different number in keyword planner when compared to the data I get other places.

I think it takes a bit more digging than that, and you also need to consider the long-tail effect from the keywords you're optimizing for.

Asking some of the clients of the business how they search or look for your products can be very helpful.

With that being said, keywords with high volume in the keyword planner do usually offer much more traffic, but also much more competition.

To Google, there is not. The R=301 at the end of the rewrite rule defines it as a 301 redirect, so it's practically the same thing. For a one-off redirect I wouldn't use the rewrite format. This is usually for when you need to grab big chunks of URLs and redirect them all at once. Still, if it works this way, there's really nothing wrong with it from the redirecting standpoint. If there was, when people used it for large quantities of redirects, it wouldn't work.

That's pretty strange. There isn't another web person there who might have cleaned things up without telling you? Or maybe your server company?

I don't see how these URLs could be indexed if they never existed, so at some point, someone created those pages and they were around long enough to get indexed. Are there any weird spikes in crawl rates or search queries since the launch of the subdomain?

I've seen this kind of hack before. The hacker just drops some folders full of HTML files into the roots. That's why all those links have a two characters sub directory. That was the folder the HTML files were in before someone likely just saw those folders in the root and deleted them. Maybe they didn't realize what they were doing and thought they were just doing the house cleaning?

Doing a "site:mshowells.com/ci/" or "site:mshowells.com/sp/" can show you what I'm talking about.

Looks like a hack. A hacker somehow got in at some point, dropped a bunch of Ugg Boot affiliate marketing pages and left. Not sure why they are 404ing unless someone already discovered these when they happened and cleaned them up. That could've happened months and months ago.

The 404s shouldn't effect your SEO, but the hack has potential to if it hasn't been cleaned up properly. Do you see a spike in search queries if you look back over the last year or two? That may indicate when the hack occurred and was cleaned up. It's important to know how the hack was cleaned up, so you can ensure that the vulnerabilities have been resolved. If they haven't been, your site is still open to additional attacks, and spam like that can hurt your SEO.

For Wordpress, it's important to keep not only Wordpress itself up to date, but also your plugins (and only use well established plugins, and do a little research on them to make sure people aren't screaming about hacking issues). Hackers search for vulnerabilities in all sorts of places.