Mark hands as you play like Harvie said. The hands where you are not sure how to play your range just mark them and go over them afterwards. Do the maths, post in forum and talk with better players. Either daily or weekly.
As for monthly review I would pick a couple of major things to work at. Could be c/r more. Defending BB more etc etc. Then review at the end of the month if you got the stats to where you want them to be. Repeat next month.
When looking at results its very tough to go into too narrow filters bc the variance is so high in short terms like a month or even 6 months. Best you can do is look at evbb/100 instead of bb/100. Im only looking for evbb/100 in all reports since its truer to your real bb/100 than the acutal bb/100 stat.
Hope this can help