You only need to register on the registration form by filling in the name, email address and information needed. of course every provider of VPS has different rules - different. I recommend to read the Terms first before registering. The 32 Free VPS Server Providers Among others:
https://secure.upcloud.com/signup (14 days free trial) <= Recommended
https://www.linode.com/ (4 hours)
http://www.cloudup.it/ (14 days free trails)
https://east1.openhosting.com/accounts/trial/ (5 days free trails)
http://www.elastichosts.com/cloud-hosting/free-trial (5 days free trails)
https://eduvps.net/
http://www.desktone.com/free_trial (7 days free trails)
http://eurobyte.ru/ (14 days free trails)
http://www.atum.com/ (15 days free trails)
http://www.cloudee.eu/preorder (6 days free trails)
http://www.cloudshare.com/ (14 days free trails)
http://www.rsaweb.co.za/cloud-servers-free-trial/ (7 days free trails)
http://www.vps.me/ (may be for more than one year)
http://www.kimsufi.co.uk/vks/geovks.xml (VKS) (may be for more than one year)
http://www.sublimeip.com/services/cloud/free-trial/ (5 days free trails)
https://www.gandi.net/hosting/trial (7 days free trails)
