I think the main question doesn't change from the main bitcoin to any little small coin and anything in between. The proper time to trade has always been during either stagnant markets like we have right now or bull markets. If the price of any coin reaches to a point that last 30 days has been over 100%+ increase it is time to stop trading it for a while, at least watch it from afar before going back in.
If something has fallen a lot recently it is exactly the same, start watching from afar before trading. The best time to trade something is while its standing still without a move or when its just going up but hasn't gone up too much.
I think the best time is when they are low and they offer something. When they are low like today than we know there is a big chance a red zone is followed by a green zone right afterwards. Nothing stays red for a long time, in the end they go up because this is the market, market can't stay red for a long time, if it wants to stay alive it needs to have both red and green, since we had the red zone now we are waiting for the green so great to buy now.
If you want to however buy something that offers something extra you can check ICO's or masternodes or staking coins and so forth so you could make decent return with them without even trading.