I noticed that there are many investors who likes to participate during ICO because of the huge profit but its very risky as well.
When is the best time to buy Altcoin?
ICO stage?
From Exchange?
Wait for the dip?
It fully depends on the stage of the market. As for now there would be much better to wait till their deep and buy from exchanges. I think that the most of alts will get their bottom after BTC suddenly grows and it will be the best time to pick them up.
But on the up-trend of course it will be much better to buy them during their ICO's, especially if the project is really good and technically strong one.