Personally I don't think there is one right way to do this. But I tend to think in terms of characters and groups. If I am worried about stuff like political events, or other large scale developments, those are all fine as long as it makes sense (i.e. I wouldn't have my nomadic hordes attack the empire from the west if it was established they were greatly weakened, but I might have them do is if it were established that something else was making them more desperate for survival). And if I did decide this would happen, I either roll out using my simplified mass combat rules or simply ad hoc assign dice pools based on numbers and organization to each side, then roll off (and I would likely ask the players to roll not telling them what it is for). A lot of times for world events I have tables I roll on at the start of each year and just put them on a calendar. And other events might emerge organically as things happen in the campaign.
But most of my stuff is at the martial world level. So if there is an organization growing in the region, and becoming a threat, I'd use my judgement and decide if any of the other sect leaders decide to take action and then what they do about it. I have something called Shake Up tables I would likely use here as well, to kind of automate this process. So at regular intervals I ask players to roll and it indicates change or lack of change in the martial world (things like people leaving one sect to side with another, one sect attacking another, sects forming new alliances, etc). The table is just a tool though so if I have a good handle on events that are happening, I will simply decide what actions sect leaders are taking rather than roll. I am not particularly precious about this though. One thing of note happening each week of play is usually enough
Mostly I am focused on things immediately affecting the party. So if they have done something to cause a problem or attract attention, it is possible npcs or organizations in the setting could be taking action against them, seek to help them, or even seek help with them. If I have an NPC who is antagonistic to the party, I am not thinking in terms of "okay an ambush happens when the party cross through the mountains" I am thinking in terms of what resources that NPC has. Sometimes I even assign the NPC to a person in my gaming circle to run remotely. Once I know the resources, I think in terms of their motives and goals and effectively have them making their moves behind the scenes or no behind the scenes as a live player in the campaign.
So in one of my last campaigns the party crossed a woman name dLady Yang, whose father they had killed while one of the players was working for him (her father was a local bandit leader). Lady Yang was very powerful but wasn't going to go after the party herself as she had lots of important matters to tend to and viewed the grudge as more of an obligation than something she was passionately pursuing. So she hire a bunch of assassins. To figure out what assassins she was hiring, I created some tables for myself (not something I think was necessary but something made this more engaging for me personally as a GM), and this helped determine whether these were singular assassins, groups, and what their levels were. Some people were existing characters in teh setting, some were made as I rolled on the table. So when they were confronted while wandering through a wilderness region int eh south by, Fa Is The Plume Smoking Assassin, it was after she had been tracking them for a time (and to do that I had her make survival rolls to follow leads to find where the party was, then I had her make survival rolls to follow the party, and I gave the party detect rolls to sense her following: I can't remember if they spotted her in advance, but I do remember they spotted many of the assassins Lady Yang sent, who were trailing them. Also if the party had been taking any special efforts to be evasive this would have been considered.
