Acquiring another citizenship before renouncing is a given, since you can't legally be stateless. How else would it work?
In any case, I've never renounced a citizenship, but I can imagine countries making it hard. Is the process itself difficult, are there requirements other than the international law one of not being stateless?
Renouncing isn't hard for most people, except Americans who have to pay thousands of dollars in fees. Acquiring the new citizenship is what's hard; most decent countries don't just hand that out.
The point is that of course you have to find citizenship in another country before renouncing your only other citizenship, otherwise you'd have no citizenship.
In any case, I've never renounced a citizenship, but I can imagine countries making it hard. Is the process itself difficult, are there requirements other than the international law one of not being stateless?