Well if your talking about a whois search.
You want to make sure you have clear information being registered. A typical scammer will just blast through the registration process and fill in anything to get past the signup pages. Usually filling out garbage information.
Most legit companies have clear info listed. Info you can use to check them out.
The other thing is the time that the website has been up. If youre checking out a chineese company then you better make sure its been around for several years. Because most scam sites are only up for a few months..
And just use common sence. If this website has every designer item from every designer manufacturer. Then they are a scammer or are selling fakes. If they have brand name electronics for more then 20% below retail then they are probably fake.
The whois search is not the only way I check out a company. I actually have several ways I check out companies to find out if they should be trusted or not.