Most importantly securing against account termination and being unable to recover that account (like it happens a lot with Google).
Also, chose a registrar that won't just terminate your account over nothing (like Google is famous to do). I've had good luck with DNSimple over the years. Sign up for their enterprise plan and make sure to stay up-to-date on their policies. If you see that they start acting "googley", start thinking about moving to another one.