Used to be that the CRM was about the only cert that meant anything. However getting certified by AIIM in ERM is also becoming more recognized. At the Federal Level getting the Federal Records Manager training/cert offered by NARA is a must - it's required in other words, whereas a CRM or ERM may not be.
The best training is experience. You have to know where you fit in an organization and what the needs of that organization are, and how you can help them achieve them. That makes a good RM in my opinion. There is no quick way to becoming a successful RM since every organization is different and you need to think of yourself as bringing solutions, not bringing problems (and many organizations view "because you have to do RM" as bringing a problem. Framing it as helping the organization manage their information (which reduces costs) and treating records and information as an asset is key, and something that can only come from experience.
For my part I'd hire someone who had been working in RM for <5 years long before I'd hire someone with just a degree in RM (if they are even offered, which I don't know. I assume they are). However that <5 year person needs to show some initiative (membership in an RM organization, a certification (even a basic one) something that shows they view it as a career.