You would think the buckle is simple but most people represent it as a square box on a thick line. A little attention to detail will make your pics looks sharper. Draw the buckle as shown here with the strap overlapping the back end of the buckle and ticking into the loop.

Here's a Quick Release buckle..used for military type characters. The strap is made of webbing instead of leather. The buckle is undone by pressing the tabs toward each other and pulling the ends apart.

Zippers are usually represented as a zig-zag if you are distanced from your character. but for close ups, try and make it like you see here. Each "tooth" is a small square with a circle on top of it..they interlock as shown here. It takes a little extra time but people notice the effort.

Snaps are pretty straight forward and you don't really get to see the 2 halves together unless the jacket is open. Again, good for detail in a close up. Show the one docking end smaller and rounded on the lip.

Sorry for the messy ovals..I can't find my template.

Laces are often represented as criss cross lines. It looks better if you draw the laces as 3D objects rather than a quick line. Show them overlapping each other and passing through the eyelets. Also, since the laces are pullig toward each other there will be buckling in the material around the stress points. Notice how I curved the material around the eyelets to show that. The tongue of the shoe/boot should push through the criss cross a little bit to give the impression that the laces are cinched down on the shoe.