They have to get together with a really neutral observer (definitely not the US) - EU reps perhaps, and then go through every little thing point by point.
The problem I see is that both sides want control of Jerusalem so perhaps there should be a joint committee of Muslims, Jews and Christians in charge of their own Holy Sites there. Possible? Probably not.
Israel is also holding prisoners without trial so they have to either try or release them. They also have to think about reparations for the land that was taken - when India was partitioned there was a scheme to give migrating people land/money equivalent to what they had lost. previously. They need to compensate the families of innocent people who have been killed and wounded in "collateral damage" since Israel was created. They also need to abide by UN resolutions and stop building settlements. People who have settled illegally in these places need to move. Any of this likely? Probably not.
The Palestinians need to call a halt to all terrorist activity and agree to co-exist peacefully with Israel. I think they will have to give up on some of their border demands. Possible? Who knows.
But one thing that does worry me is that even if a peace plan is ever agreed on, there is no reason why Israel, with it's huge arsenal and US-aided army will not seek to expand its borders.