To my knowledge, you don't have to have an AOW to complete a Rescue course. Many people take it right after OW actually. As far as number of dives, I'd recommend probably at least 10-15 just so you can make sure you're comfortable in the water. It's meant to challenge you and to teach you to stop and rationalize things in the event of a situation rather than panic. Rescue isn't so much about learning how to rescue other divers as much as it it about situational awareness and self-rescue. It focuses on teaching you how to recognize distress in other divers during all phases of a dive (before, during, after) and how to handle and/or prevent situations that could arise as a result. Of course you'll be rescuing panicked/unconscious divers, too, but that's only a small part of the course.
Skills to make sure you're proficient in:
-Buoyancy (doesn't have to be perfect but should at least be able to stay somewhat neutral within reason)
-Mask Skills (including being able to dive w/o one)
-Air Sharing
-Most importantly ***Be able to maintain your composure in any situation***
Can't stress that last one enough. Regardless of what happens before, during, or after a dive, be sure to remain calm and collected and don't panic. The rest will come easy.