You should ideally begin with a weight that you can complete around 20 repetitions with normally, which typically represents 60 % of their one rep max for most people. (fitnessandpower.com)
For me: try to set a new 1 rep max on whatever form of front squat I was doing. (rugbystrengthcoach.com)
To optimize this method you should do a one rep max test so that you know what weights to start with. (gymjunkies.com)