Take clones as soon as you have enough plant mass to allow removal of slips without undue stress to the donor.
Label each donor and all associated slips carefully.
When you flower the donor, you will know which clones to save. Choose the clones from only your BEST female (decide this after harvest and cure) to carry on the line.
You can take clones in flower but it is stressful to the donor and a waste of time to do as anything other than an emergency measure, since you have to wait up to a month for reveg before flowering, and chances of hermis are higher.