If it is a new series that you want to start recording when it starts airing in the future, a common situation in our home, then you don't need to use a "record by time" rule.
Just do as you have done, and change the search rules, and rename the rule to something more meaningful.
For example, if there was a new series starting in a few weeks called "Castaways", just select any program in the Guide (in Standard View works best for this), subscribe to it, then edit the subscription to change the default recording rules to search for a Series or Name of Castaways, and change the rule name to something like "New Castaways Series". Plus change all the other rule parameters of course.
So basically, yeah, you did it correctly. There is no separate "Create a new blank subscription" function in MC.
If you are just learning how to set up recording rules, make sure you learn about AND / OR rule joining using the different types of brackets, and check out everything in the Edit Rules dialogue. Be aware of the how the "Do not record reruns" (needs the rerun or repeat flag in the EPG data) and "Do not record programs that have been recording in the past" (matches to a set of fields from the EPG which must have values and be unique to work properly) work, and the data they depend on.
There was a lot of discussion in the forum when the new rules functionality was added a while back, and there may even be a Wiki entry.
