Unless it's a great domain and then .net is always my favourate as a "lucky loser"
Or .info as a "lucky loser" if the INFO has any relavence to the domain name of course.
Pretty much everybody defaults to .com when thinking about websites. There are some exceptions, ie. I have done sites for people here in the UK who chose the .co.uk suffix to make it clear they are a UK based company.
.com is first but if u didnt got the name you are looking hten you go with other extensions
a good anme is required and it should easily to remember for visitors