Suit trousers should meet with the tips of your shoes - preferably with no overhang that risks you stepping on the cuffs. For a more modern style, you might prefer an inch higher, to show a slip of the (hopefully matching!) socks.
Suit trousers should fit the waist comfortably without requiring a belt, with enough free fabric to move easily - even if it’s a skinny fit, it shouldn’t feel too restrictive. While looking great is always a positive, comfort is generally key.
Start by turning the trousers inside out and ironing out the hips (following the pocket bags) and the waistband - then, turn them back to the proper way, lay the trouser legs atop each other and iron them across for a good, strong crease at the sides.
Fold the trousers in half, so the legs run together, then fold this up to the waistband.This prevents excessive creasing and takes up minimum room, ideal for suitcases.
Suit trousers should sit higher than jeans - just above the hipbone, or even higher dependent on the fit. Jeans are designed to be much lower.