Sometimes, when the price of a coin is expected to go high like when Tesla announced Bitcoin acceptance it went higher and that is where I usually invest knowing the price will rise and sell once the market hype is over. People did the same with dogecoin but I usually avoid such instances because dogecoin doesn't have a futuristic value anywhere close to bitcoins, so in case I make a mistake in reading the market, I can come out still profitable in bitcoin but not dogecoin.

Very rarely to be honest because most of them are scams.

I don't usually make a firm strategy or anything like that. I just watch the market and follow all the news regarding upcoming coins and when I feel like a particular coin is worthy of some investment, I just do it.