The logs plugin only requires the function name you want to fetch the logs for. Other than that there are other options that you can add for extra control. Here's the full options list:

--function or -t The function you want to fetch the logs for. Required
--stage or -s The stage you want to view the function logs for. If not provided, the plugin will use the default stage listed in serverless.yml. If that doesn't exist either it'll just fetch the logs from the dev stage.
--region or -r The region you want to view the function logs for. If not provided, the plugin will use the default region listed in serverless.yml. If that doesn't exist either it'll just fetch the logs from the us-east-1 region.
--startTime A specific unit in time to start fetching logs from. You can use standard date/time (ie: 2010-10-20 or 1469705761), or simply a "since string" like 30m (30 minutes), 2h (2 hours), 3d (3 days) and so on. We'll just fetch the logs that happened since then.
--filter You can specify a filter string to filter the log output. This is useful if you want to to get the error logs for example.
--tail or -t You can optionally tail the logs and keep listening for new logs in your terminal session by passing this option.
--interval or -i If you choose to tail the output, you can control the interval at which the framework polls the logs with this option. The default is 1000ms.

Examples

serverless logs -f hello --startTime 5h

This will fetch the logs that happened in the past 5 hours.

serverless logs -f hello --startTime 1469694264

This will fetch the logs that happened starting at epoch 1469694264.

serverless logs -f hello -t

This will keep the terminal session listening for logs and display them as they happen.

serverless logs -f hello --filter serverless

This will fetch only the logs that contain the string serverless