I learned how to heckle and was at the top of my heckling game during bad times for the teams I followed. The Giants and A's were both bad in the early and mid 80's. When the crowd is small, heckling is easy because everybody can hear you. But when there is a large crowd it is more difficult because the ambient crowd noise is so great. When your team is winning and all the games are sold out, it's usually loud out there.
Sometimes for large crowds, I would get a feel for how a crowd reacted to heckling. If the crowd were noisy enough, my strategy changed from yelling loud to getting others to do the yelling for me. If there were enough instant-asshole-just-add-water types around me, I would yell (unexpectedly for them because they weren't regulars there) at a player. Those fans would laugh. I would yell again, and if any of the other regulars added something, those fans figured out that yelling at the visiting player was a community thing and they joined in. Instead of yelling louder to overcome the crowd noise, I could save my voice for the next game by getting others to do it for me.