Don't create hard maps. Hard maps are annoying for most people, and when they see a hard map, they just leave.
A hard cj isn't fun. Try to make something more original.
Some people can't do obstacles like this (http://prntscr.com/plkg5f) or this (http://prntscr.com/plkh2b)
Try to don't put a wood, dirt, grass, etc., with 0 friction. It's better you just put an ice.
Be original. We don't accept maps with obstacles very seen in parkour.