There isn't much to add to Garnier's list, but there are a couple of other things which I used in a desperate attempt to rescue my withering Serbian empire.

After choosing the general whose responsibility was to renew the Serbian royal family, I of course gathered as many armies lead by disloyal generals as possible and gathered every loyal unit into a single province.

After that I simultaneously attempted to assassinate 4 of the highest ranked generals and declared war with about 4-5 allied factions. As attacking your allies causes the rulers influence to drop (one point per nation, IIRC) this along with the assassination attempts caused a nice civil war.

I naturally chose freshly recruited 0-valour assassins to prevent any unwanted casualities from happening among the generals. When declaring war to allied factions try to choose "safe" options that won't take advantage of your weakened condition while you stabilise your empire after the civil war. (Ireland is a safe option, avoid any neighboring factions if possible.)