If your aircraft has minimum instrumentation (basically RPM only, plus your own ears), leaning until the engine runs rough and then enriching until smooth running is re-established, is virtually the only way of leaning for best economy. As you've seen, 50 rpm lean of peak may already lead to a rough-running engine.
For best power, lean to max RPM. But do NOT lean the engine if it's producing more than (about) 70% power. (The exact figure will be in the POH.) This generally means that you should not lean for best power below 3000-5000 feet (again, depends) otherwise you cook the engine: It needs the cooling effect of the evaporating excess fuel. (Leaning for best economy can be done at any altitude, as the engine will be producing less than 70% power.)
Now if you have more instruments, like CGT, EGT, per-cylinder engine monitoring, Gamijectors, lean-assist G1000s, you name it, there's a lot more you can do. Likewise, the leaning techniques for a variable pitch/constant speed propellor are different but these types of aircraft tend to have more sophisticated instruments than a single RPM in any case.