Domain thoughts
 

I was researching a domain name. The .com I wanted was taken, and used for a very unprofessional website that would be of little or no competition.

Would you go for the same thing in the .net or would you go for something totally different?

Well if you are not worried about competition then I would just go with the .net ... The domain name is important but not vital.

In addition you can always add more domain names and point them at the domain you choose so you cover more bases.

If it is a branding thing than ofcourse you will want your very own domainname that is not in use on a .com .. If branding does not matter then I would not be worried about using the .net when someone is already using the .com You may even get some of the traffic meant for that site when people put in the wrong domain..ofcourse you may lose a little too for the same reason.

If you advertise it well (eg Google paid ads) you don't have to worry about anything.

Edited: So go with .net but avoid .co

If it's for seo or some marketing website or something small then Yes, sure I would go with other extensions e.g. .net .org .biz or .info...but if it's for something with brand in mind or something more serious then No. I would try to go for .com + a few additional gTLDs if possible.