i just realized that after reading all these guides on trimming, topping and training that they always say to stop doing so two-three weeks before flowering. problem is that i don't know when 2-3 weeks before flowering is. i know how to tell whether or not a plant is flowering or not, just not when in the future. any tips on this guys?
my suggestion to you is to read a lot more. when you switch the light cycle to 12/12 the plant will start to flower indoors. outdoors it depends on the season, typically in most of the US states you plant now and then the plant will start to go into flowering in about August, and you will harvest in late September and October. so are you indoors or outdoors?
You don't need to stop training or topping weeks before flowering. Topping you should stop by the start of flowering, and training you can continue doing all through flowering (though into flowering is a little late to start training).