LOL, I had indeed suspected there were quite a lot of us using Amazon EC2 for Yacoin mining. I just shut down most of my instances as well, including c1.xlarge's in the Virginia data center.
First, you need to start a single instance of Ubuntu 12.04.1 LTS, either for server or cluster - doesn't matter. Then SSH into it (don't forget to set your security settings to allow your SSH!). I'll add the detailed instructions for this later - but honestly, AWS is pretty simple, I think anyone can figure it out.
Once your SSH connects, enter the following 3 commands in sequence:
Alternative approach, or at least this is what I did, get one instance all nice and set up, with /etc/rc.local firing up yacoind. Pre-seed yacoin.conf with the desired options and addnode= options to form your own highly interconnected low-latency mesh within the Yacoin network, run yacoind to create the wallet.dat file and download the blockchain. Then stop the instance, create an AMI out of it, and then proceed to spawn massive numbers of spot instances off that AMI. All of the instances then mine to the same wallet mining address, automatically when they boot up, with no need to individually SSH into them. Pretty nice now that Amazon lets you copy AMI's between their data centers.