Rehearsing The Eulogy
The more familiar you are with the words, the more comfortable you will be when delivering the eulogy.
As mentioned, don't expect to commit it to memory. Even if you think you have it down, the stress and emotion on the day may throw you out. Also, looking at faces in the audience can give you an emotional reaction and it can be handy to have something to refer to, to stop that happening.
It's okay to go back - you only get to deliver this once and you don't want to leave anything out. And don't worry if your voice breaks or you have a few tears or you lose your way. This audience is behind you 100% and quietly thankful you are doing the job and not them.
Onto the delivery…