Use this guide to always win spleef. Disclaimer: This will take the fun out of spleef but you will win.
Step 1: Set Your FOV to Quake Pro (Maximum)
Literally turn your POV up as far as it will go to get a higher field of vision. This makes the next step easier.
Step 2: Go Into 3rd Person Mode (Press F5)
Go into 3rd person mode so that you can see around you which blocks are still there. This makes the next step considerably easier. You can also see if someone is in your pursuit.
Step 3: Run and Parkour the Missing Blocks
Just run around and parkour all the holes. The goal is not to spleef because that gets you killed. If you want to always win, you need to sacrifice fun.