I actually try not to have a default - to mix up the campaigns to make them distinctive. Indeed, for each campaign I try to introduce a unique "side dish" (to go with the Orc&Pie) - something to hopefully engage the players in the Social and/or Exploration pillars of the game. One campaign might be about uncovering secrets, another about seeking out lost civilisations, another about political intrigue, and so on.
I do have a default structure I use, which is an Closed-Open-Closed approach - the campaign will generally start with som fairly tightly-constrained inciting event/mini-adventure, then will open out into a much more sandboxy section. Somewhere in there the characters will find a locked door (literal or metaphorical) and a bunch of keys, leading them to come to a fairly constrained end point. (Sometimes, the structure is Closed-Open-Closed-Open-Closed, or even more iterations. The idea is basically the same, just repeated.) I pretty much got that structure from the 5e published adventures, notably Lost Mine, Storm King's Thunder, and Curse of Strahd. While I find many of the 5e campaigns lacking in execution, I really like the way they're mostly structured.