Before you park any domain names, you must focus on finding hot keywords that buyers would be interested in. The best way to make sure you get a good return on your investment is to pick a domain name with acceptable traffic, somewhere around 10,000 searches a month. You can do this conveniently by using tools like Google Keyword Planner or Niche Finder Software.
I've seen some people comment about losing the link value of domains that have expired and picked up, but what about non-expired domains?  Let's say a competitor is going out of business and they still have a year or two left, and we buy their domain and site.  Is there a risk changing registrant info and registrars, even if I keep their site up and mostly the same as before?  I was under the impression that I'd want to keep it under their name so as not to hit the uber-reset button on the domain's inbound link value.

Yes, we port in all of the domains from NameJet, SnapNames, etc. There are a lot of great deals to be found. Some are absolute trash of course but if you can sift through them and put some time in (hopefully that is what we are trying to do with our tools is save time and give some value add with the SEO metrics, alerts, etc.) then you can find some great bargains.
Just because a domain has expired, doesn’t mean it has to be kicked to the curb immediately. It is worth considering turning the internet address into a parked domain for a certain period of time in order to generate advertising revenue. This allows domain owners to bide their time and come up with a new web project for the domain or to find a suitable buyer.
In order to maintain ownership of a domain, you must renew it yearly. If you don’t, it “expires”. An expired domain goes through several stages before being released again for general registration. The process differs slightly from one registrar to another but it’s more or less the same. GoDaddy explains what happens to domains that expire with them here.
Contact Potential Buying Companies: With my domain IHateCold(.com) I will email the marketing teams of some of the large winter clothing companies and let them know of the available domain to buy and a few potential slogans they could use with the domain name. This is a very “I’m here to help you” scenario that I’m curious to see how it plays out. They’ll have to learn about the domain name for sale somehow, right?
In the past, expired domains were used as part of black hat SEO in order to generate backlink sources quickly and easily, and this practice is still used somewhat today. Getting links in this way is not a recommendable practice. All relevant search engines work nowadays with highly complex ranking algorithms, which can no longer be outsmarted by these link networks.
Length: This is pretty self-explanatory. Generally the shorter the domain name, the more valuable it is. This difference in value decreases exponentially as the name gets longer, though. For instance, the difference in price between 3 and 4 letter domains are significant, while the price difference between a 7 and 8 letter domain would usually be much less significant.
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