1. Turn in the proper direction - "the pedal in question" does not tell us which one. If the left one it comes off clockwise (reverse of normal)

2. Use a long pedal wrench or a cheater/extension bar or pipe on a shorter (but strong) wrench. Or just go down to the bike shop and have them remove it.

3. There are additional things one can do (Kroll, heat) but most are not necessary.