Question: So far playing I haven't done much in terms of personal unions. What are the methods of gaining a PU, and lets say as Austria, how do I go about manipulating the world so I get PUs I want? I checked the wiki for this info with no luck, and I was hoping to hear some of you guys' PU focused playstyle strategies.
Note you need to have a royal marriage with the target country.
Wait for the target country to have a low legitimacy heir or no heir at all, then claim the throne. You then immediately start a war with the claim throne casus belli, to forze the personal union you need something like 70+ war score depending on the size of the enemy country. Also don't forget to get relations over 0 or the personal union will break when your ruler dies.
Countries with more armies than you will insult you so be sure you have more armies than the country you whant to forze into a personal union.