I used to have to split my boil before I got a turkey fryer. The ideal way to do it would be to evenly divide the runnings, so that both pots had roughly the same gravity/make up and then divide the pot. Something like 2/3 of the first and second runnings in the bigger pot, then 1/3 of both runnings in the smaller pot, and then divide the hops like that, too. 2/3 in one pot, 1/3 in the second pot, and then cool them both and mix in the fermenter.
The easiest way to do it might be to draw off your runnings into a third container- like your ale pale with gallon markings. That way you can divide it easier.