Well, I've been trading for a few years now on several exchanges, and while I still consider myself an amateur in this field, I've learned some valueable lessons ... ! I'll kick off with a cliché:
Never invest more than you're willing to lose: personally I've never 'invested' more than a few tens of bucks, but I've seen others enter the market with an unhealthy amount of money and get burned mercilessly. Especially in the volatile world of cryptoland, your stake can burn up almost completely in a matter of hours. It isn't a bad idea to consider the amount you're investing as lost, so you won't get mentally hammered when you're actually confronted with red numbers.
Don't trade with emotion: FOMO, panic-buy, panic-sell, etc ... In my experience you'll mostly end up in the red numbers if you don't consider things rationally. Emotional trading can - for example - lead you into an ordinary pump & dump or you might sell of crypto too early. Deploy a strategy and stick to it ... !
Don't take advise from others: do the research yourself and then decide wether you're going to invest or not. The world of cryptocurrencies is incredible volatile and its almost impossible to predict what's going to happen next. Well ... the general trend is upwards for crypto as a whole, but that doesn't guarantee you're NOT going to get burned.
Diversify your investments: well, it makes you less vulnerable if a certain coin suddenly goes into a nosedive. Again, this doesn't guarantee a profit, but the chances of your investments getting wiped out are smaller this way.
Please note that I don't want to come across as some arrogant smartass who knows it all. As a matter of fact, I've made mistakes regarding all four points mentioned above up to a few weeks ago ... ! But I do know these raised points could increase your chances of success in the world of crypto.
Seeya ... !