What should a guy do before getting married and before getting engaged to protect himself and his assets?

For example, like if I couldn't stop my younger brother from wanting to get married but I could give him advice to follow. I know at the very least one should give clear expectations to the woman that a prenup must be signed but I also know you have to mention about that far in advance (because legally a prenup can be invalidated if it is signed too close to the marraige date) and what else should a guy do?