The best time to buy is when people think that it's boring to invest in crypto or if there is too much blood on the streets as we have been hearing since our early stage, so it's better to first decide when to buy and then decide a specific target for our own, be it the bull run factor or the normal spike in the value of BTC. It's always better to DYOR and to look for many factors before selling.
I'd advice not to sell at good news alone because since we began, we have been following: buy the rumors, sell the facts. So always wait for a spike after the dump that takes place once the good news is released, so that you make enough from your investment.