Regular cotton trousers might be the easiest thing to combine with a sport coat, but denim can work equally well. In this post I'm going to point out three factors that are the key into a successful sport coat look with jeans - the type of jacket, accessories and the fit of the denim.
First, the fit of your jeans. This is pretty basic, but I'd say it's quite common to see people wearing something that I'd call skinny fit jeans with very low rise with a jacket. Now, this is going to pretty basic fit 101 stuff, but something that cannot be stressed enough. Denim, as all other clothing, usually look the best fitted but not too tight. What's even more important when you put on a jacket is the rise of your trousers. Low rise trousers or denim will not look good and all the proportions will look off. So invest into denim with proper grown man's rise and pay attention that there's enough room (but not too much) for your thighs and calves. Also forget washed denim.
More on denim here.
Then, the type of jacket. You are going to want an unstructured (or very very lightly padded) jacket that has an intresting and at least to some degree informal fabric. The unstructured linen jacket with patch pockets here is a good example. For fall and winter keep the same things in mind, but naturally adjust with the season. An example for slightly colder weather can be found here and here.
Finally, accessories. First up, you're going to want to avoid any shiny silk pocket squares. Stay in casual fabrics with interesting textures, cotton or linen for summer and perhaps wool for winter. If you wear a tie, keep to the most casual options - knit ties. In this case, I've gone with a navy Berg & Berg bubble knit tie and a lightweight cotton pocket square from Drake's London. The shirt has also been picked to have enough roughness or texture to go well with the outfit and to finnish the look I've picked a beautiful braided leather belt from Berg & Berg instead of solid leather belt.
And then, it's often perhaps the best idea to not wear a tie at all, but the same "rules" still apply. A tieless example here.
So, leave a comment if you disagree or think I missed some essential points. And enjoy the rest of your Sunday, more stuff will be published next week.