It depends on the the last star waypoint. I know your going to hate to hear this, but you've got to have the chart for the particular star you are flying...you can get just about any US chart at Airnav.com there is usually a waypoint that says "expect to cross [waypoint name] at such & such [altitude] (with or without a speed restriction) copy that info into your legs page. That should give you enough time to setup for any runway approach since that waypoint is designed so you're at the right altitude and speed for vectors to final to any of the arrival airport's runways. I'm over simplifying this a bit so if you have more questions I'd be happy to help again.

Happy Trails!

Bob