1. If you meant about crypto that got delisted from exchange site and it's better to not buy it as it will become another abandoned coin

2. If you meant about a new token before it will be listed in exchange site and then you can try to buy that when ico will begin. The only question is whether you have been agreed to deal with the risk? i meant when you're buying a new coin and then you may get a good ROI or otherwise you will be loosing your money when it will be losing its value as it will be traded below the ico price.

You can buy that through participate in the ico sale or private sale which will give you to buy coin before it will be listed in exchange site. There are bunch of tutorials in internet about how to participate in the ico.