There's a few things that can make sure a speedrun comp works well. Off the top of my head, these are the key things to keep in mind.
1) Establishing a community that's interested in the game
2) Some sort of in-game timer or equivalent for easier timing
3) Clear communication on rules (especially for where and how runs are submitted)
4) Good Tutorials (Unlike mine)
I've only done this once, but that's what worked well for me! Let me know if that makes sense or if I should clarify on any of that. Good luck with your game!