Leather trousers hold heat the second you sit down somewhere warm, and they'll show every mark from a bag strap or a wet seat before you've even noticed you've sat in something. That's the warning. The reason they're still worth having is the way they move when you walk, the slight drag and give that no other trouser gives you, and the fact that a good pair makes a plain jumper look like you've made an effort without actually making one.
The limits are worth being honest about. If you're spending all day moving between hot rooms and cold ones, meetings, buses, school runs, they're not the easy choice, real leather doesn't breathe and faux leather breathes even less. They're also not a pack-light holiday trouser, they crease in a bag and sulk about it. For sizing, go by hip and thigh rather than waist, because leather doesn't have the forgiveness of a woven cotton, there's no settling in over the day the way denim softens. Too tight and you'll feel it by lunchtime, too loose and they bag at the knee within a week and never bounce back. The classic fit mistake is buying them a size up for comfort and ending up with a saggy seat, when what you actually want is snug through the leg with enough room to sit and bend without a strain line appearing across the thigh. Cheap pleather will crack at the knee crease within a season, you'll see fine white lines where the coating's given up, while a proper leather or a well made faux version keeps its surface and actually improves with wear, gets a bit of a shine at the places that move. That difference shows up fastest at the knee and the inside thigh, so check those spots before you commit, not just how they look standing straight in the mirror.
Keep them away from anything else shiny or stiff, a patent boot and a leather trouser together reads like a costume rather than an outfit, and a heavily structured blazer on top can tip the whole thing into try hard territory. They also don't want to share space with another heavy texture, a chunky cable knit fights the trouser for attention rather than letting it sit quietly underneath. Soft knits, silky shirts, something with a bit of drape, that's what lets the leather do what it does best.
Sit down in them before you buy, not just stand, that's where a bad fit actually announces itself.