If there are more than two, the last to touch the choice gets it. This is where each person looks at the divisible good and takes off some to make it fair. Last person to touch the good gets it. It seems to work well.

When there are only two to make the choice, the “I cut you choose” method works best.

There's a whole field of discrete math around fair division. This is one is called divide and choose.

And if the resource is not continuous, or there are more than two parties:

https://en.m.wikipedia.org/wiki/Category:Fair_division_protocols