Quintilian: Rules of thumb for a proper "Dispositio"

Remember that after inventio comes dispositio:

... in speaking, however abundant the matter may be, it will merely form a confused heap unless arrangement [dispositio] be employed to reduce it to order and to give it connexion and firmness of structure. Institutio, VII, Pr.

In Russell translation:

But just as it is not enough in erecting a building simply to collect the stone and the timber and the other building materials, unless the hands of craftsmen are put to work to dispose and assemble them, so also in speaking, however rich the material, it will be nothing but a random accumulation unless Disposition organizes it, links it all up, and binds it together. Institutio, VII, Pr.

Watson translates confused mass.

Book VII, Pr. 

I used also to employ the following method [for arrangement]. I went back from the ultimate species (which generally contains the vital point of the case) to the first general question or descended from the genus to the ultimate species ... But in our search for such questions we follow an order quite different from that which we employ in our actual speaking. For that which as a rule occurs to us first, is just that which ought to come last in our speech... We must not be therefore be content with the thoughts that first offer themselves, but should press our inquiry further till we reach conclusions... Consequently after surveying our opponent's proposition, an easy task, we should consider, if possible, what it is most natural to answer first. And, if we imagine the case as being actually pleaded and ourselves as under the necessity of making a reply, that answer will probably suggest itself. On the other hand, if this is impossible, we should put aside whatever first occurs to us and reason with ourselves as follows: "What if this were not the case?" We must then repeat the process a second and a third time and so on, until nothing is left for consideration. ... The rule that we should descend from the common to the particular is much the same, since what is common is usually general. ... I used also to note down separately whatever was admitted both by my opponent and myself, provided it suited my purpose, and not merely to press any admissions that he might make, but to multiply them by partition, ... I used also, with reference to the whole material of the case, to do what I have already mentioned as being done with arguments, namely, after first 
setting forth all the facts without exception, I then disposed of all of them with the one exception of the fact which I wished to be believed. .. Let us therefore consider every possible point; for thus we shall discover what is the best line for us to pursue, or at any rate what is least bad. 

References
here