This one is a relatively complex question; success in the sense of the word was a rare thing for the Hapsburg Empire in it's late Dual Monarchy period. In fact it was the lack thereof that required it's creation. Lets go back to 1867 for the foundation of the late Dual Monarchy.

Things had not been going well for Austria at all. The large Empire which was primarily administered by the Catholic and German population of Austria proper was in all senses collapsing. Positions they had gained in 1815 at the congress of Vienna within Italy and Germany had fallen to the combined interests of Sardinia - Piedmont and Prussia. Both of whom attacked the Hapsburg monarchy and undid it's interests in South Germany and the Italian peninsula through the Austro - Prussian War. Where the Austrians suffered a humiliating military defeat in their Czech possessions at the Battle of Königgrätz and were expelled from their most important cities in Italy. Austria in it's current form was at that point moribund and set to lose it's status of great power. This is where the timely intervention of Count Friedrich Ferdinand von Beust is extremely important. And it's where the roots of a more diversely ran Austria - Hungary lay.

Count von Beust was a firm opponent of German Iron Chancellor Otto von Bismarck. And was both appalled and alarmed at the creation of a Greater German state that isolated and excluded Austria - Hungary. He dreamed of avenging their defeat and restoring Austria as the premier German state. He was appointed Foreign Minister (Despite being a Saxon Protestant) by Emperor Franz Joseph to work something out to get the Hungarians on their side. To do so therefore would require compromise to the Hungarians and a series of promises on the behalf of Austria that would at best destroy most of their influence beyond the borders of the Hungarian realm with the Hapsburg Empire.

Hungary by this point was extremely demanding of an increased role in the Empire or more self determination. Hungary itself having rebelled in 1848 in a precursor to the buildup of Austrian woes. These demands now seemed much more reasonable; especially if it could placate their most unruly minority and turn them into an ally for preserving Hapsburg status in the world.

Therefore, on the condition the Austrian Emperor also be separately crowned King of the Hungarians and also that the Hungarians may reopen their own parliament in Pest. The Hungarians agreed to become the second nation that constituted the Empire. Therefore the Austro - Hungarian state can be defined as a diverse one.

However it was not by the standards implicated in the title. Hungary once added to the Imperial decision making status was firmly against any other nationalities (Particularly the Czechs) being incorporated in that manner. Hungarian reactions to any plans to expand the representation of ethnic groups in the Empire was always rather volatile. And in one case resulted in the resignation of the Austrian half's Prime Minister! (He attempted legislation to incorporate the Czechs on a similar status. This was opposed by Count von Beust himself who regretted what had occurred with Hungarian powers.)

In addition; the splintering of the Empire into the two de facto power blocs ensured that Imperial ambitions would always be opposed. (The Hungarians often refused any ideas of war that was Austrian in design and also refused to incorporate the army. Leaving the Hungarian portion by the time of WW1 lacking in some fields that the Austrians had developed fine when they reached the Italian front to horrible effect.) Hungary also firmly oppressed minorities in Slovakia, Transylvania, Vojvodina and Croatia which fell under their administration.

Despite using Hungary as an example for that. Austria was rather similar in it's actions. They refused autonomy for the Slovenes, Italians and Czechs in their portion of the Empire and worked with the Hungarians to limit any influence from the largely Polish/Ukrainian Galician realm which was probably the best example of what you were looking for in a recipe of success.

In a sense as well. Nationalism was always a pressing issue on the imperial realm. Nearly all nationalities prior to and following the Dual Monarchy wanted independence. It was just that the Austrians gained the assistance of the Hungarians in capping this nationalism off. The real reason it never began to crack until WW1 was the strong character of Kaiser Franz Joseph and the support in oppressing member states Austria got alongside Hungary. Very rarely was anyone outside of the Austrian or Hungarian nationality made a prominant member of the Imperial Government or Army. (Baron Boroëvić von Bojna, a Croat and last field Marshall of the Hapsburg army may be the seldom exception.)

This really shows because the Empire began to collapse following the death of Franz Joseph by 1916; everything beyond that was Austria - Hungary becoming totally in a sense subsidiary to the German Empire for survival. German commanders and troops ensured that the Empire did not break up until they too start experiencing severe problems on the front. In October 1918, at the battle of Vittorio Veneto, soldiers of all nationalities just started deserting and marching home. Shortly after the Empire was forced to dissolve itself and by that point most of the nationalities already broke off unilaterally. (Czechs and Slovaks on October 28, South Slavs on October 29, Hungary on October 31).