Seeing as we are getting some activity with mapping, I thought I'd share my thoughts on some gameplay guidelines. These are only my own opinion, so don't take these as "your map wont get verified if you don't follow guidelines".
1. Have multiple routes, that are balanced to be approximately equally as fast (give or take 0.2). There's so many tricking techniques players can use, that it's bound to happen that some people prefer i.e. crouchsliding over halfjumping, or walljumping over ramps.
2. Never compromise gameplay for the looks of the map.
3. Optimize the map for as many as possible gamemodes available.
4. Avoid making spots where players need to clearly slow down in order to be able to do it. These include the infamous drop-downs and narrow turns. No one likes to first build up speed only to lose it all and start all over again, in a same run.
5. Avoid making platform distances so high that players need to loop around the same platform to reach next one. This also includes the cheap way of prolonging the run by putting a checkpoint to a place that players need to go through twice.
6. If you have holes between wall and trims or such, clip the holes. Otherwise rocketjumping becomes really annoying as players might unluckily shoot through the hole and not receive as much boost as expected.
7. Keep ramp sizes relatively small to block sloperun+release in unwanted places.
8. Don't put too many holes in the floor. It's perfectly fine to force your route by putting some well placed holes in the platforms, but popular maps are the ones anybody can finish.
There's probably more, but these are the ones in most clear memory at the moment. Feel free to share your opinions or your own guidelines. Also note that I don't use these guidelines in all of my maps, as sometimes you just want to do some speedmapping, but in general I try to remember most of the mentioned above.