Here is a simple hack for making your pedals work better.
Problem: The spikes that grip your shoes on mountain bike pedals are bent forward so they don't grip.
Solution: Use a vice grip or pliers to bend the spike forward.
Note: This will only work for pedals with metal spikes. Don't bend back and forth many times or the spikes may break. This worked fine for me but i am not responsible if you break your pedal(s) doing this.