Will need to consider the following:

• Instance Type
• Security Group
• Keypair
• Availability Zone

Keypair

Use the 'ec2-add-keypair' command to generate a keypair with a name of your choice.

You DO NOT need to generate a new keypair each time.

  ec2-add-keypair supersecure-keypair > supersecure-key

Launching

For this example we'll launch our instance with default security group, instance type and availability zone

    ec2-run-instances ami-1cd73375 -k supersecure-key

This launches the latest Ubuntu 8.0.4 32 bit from Alestic.com