I'm new to AWS, just setup a ubuntu ec2 and I've made a security group which allows me to ssh in and that's about all for now. What do I have to do to make it so I can also ping my instance?
You have to make sure it allows ICMP packets to be seen/not firewalled.
Just go to the security group for the instance, click on the "inbound" tab, choose "Create a new rule" dropdown and select "All ICMP" and then click +Add Rule, then click Apply Rule Changes. The change takes effect immediately.