Big bonuses at ICO. You buy tokens for $50 and get 40% bonus. When the token get to the exchanges you have tokens for $70 so you can sell the tokens with the price of the ICO (first day on the exchange) and get $70 (40% profit). People panic, they begin to wonder if this is the next shitcoin, they begin to sell their tokens, the price drop and if you think that the project has future, you buy tokens with the $20 (your profit from the ICO) and in most cases you buy more tokens with the $20 than you had from the ICO.
pp. this only work with projects with passable white papers. If the project is really good, you won't see big dump at the first opportunity and if the project is a scam you lose your money.