Maybe this isn't quick, but how does plotting work exactly?
I only had time for 2 quick games last night, but in both of them I got to around 15-20 provinces.
No one asked me to join any plots and no one joined my plots (as far as I could tell
A few years before I wanted to attack someone I would make a plot. Eventually I would get tired of waiting and attack them. I would succeed, but the plotting did not appear to help in any way. Some people did pile on my enemies once their armies were killed, but that did not appear connected to the plotting.
Can anyone give me a 10 sentence FAQ on plotting?
Firstly, there are basically 2 kind of plots, the first kind is when you are an independent clan and want to plot against a rival clan. The second type is to plot to break from your own clan, either in a civil war when you are the pretender or when you are a powerful daimyo or clan leader of a different dynasty.
I will talk about the first type, as it is the one I've experience with (never played as someone who is not the clan leader). You first activate it from the plots screen, choose the clan you want to plot against (you can only start plots against your neighbours this way). Once the plot is started you get a new diplomatic option for other clan leaders or daimyos.
Now you just need to invite them to your plot. Other characters are somewhat picky on when they want to plot. The first issue is their honor, they will not plot if their honor is low (depending on the character, anywhere between 45 and 60 or more), then, they will evaluate their relations with you and the plot target, if they like the plot target more than you they won't plot. This one is tricky since some clan leaders have such godly diplomacy stats, and that might prevent you from ever reaching an satisfying relationship score.
In order to increase your relationship with the invitee you can basically take three actions: Gifting, Marrying and Increasing Relations via the Master of Ceremonies. Send your MoC and when he succeeds, quickly gift the target of the invitation to stack both bonuses.
You can also try to lower the relations of the invitee with the plot target if the fist is a vassal of the latter. For this, either sow discontent and try to lower the plot target's honor through ninja actions.
Then there is opportunity, other clans won't be willing to join you if they are already at war, or for some other reasons they won't share with you (I suspect if they are already plotting against someone). These are hard to influence.
With all these said, plotting is not a guarantee, and requires patience, sometimes your leader is just too shy, or the enemy is on a strong position. Wait for the right time and you will eventually succeed.