The SimpleStrategy is a basic replication strategy. It's used when using a single datacenter. This method is rack unaware. It places replicas on subsequent nodes in a clockwise order.
Here is a sample CQL command to create a keyspace with SimpleStrategy and a replication factor of 3, which can be fired from the cqlsh prompt:
cqlsh> CREATE KEYSPACE cassandrademodb WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };