1) Avoid anyone that guarantee you 100% gains. Those people are trying to push you into a ponzi scheme, sell you a course/subscription or straight scamming you. Think for a moment, if they know a 100% way to make money, why they are not doing it and wasting their time on getting you on-board. Probably because they want to make money out of you, don't you think?
2) Don't buy into hype. I know our brain is wired the way that when everything is going well we expect that it will keep going this way. But higher something is risen, higher is the probability that who bought before the hype will start to sell and realize their profits. This internally generates pullbacks that often end up in creating panic and liquidations driving the price even further down. Therefore when everything is green ignore your greedy brain and sell if you have some holdings once it reaches your initial target and don't buy if you don't hold any. On the other hand when everything is red and the price was falling for a week or more is probably the best moment to buy despite your brain will make you feel bad about it.
3) Don't invest everything in the same coin. Diversification is the Key to survive in this volatility jungle. Sure if you go all in on one investment and it goes well you can hugely increase your portfolio, but at the same time is the easier way to lose everything. So it is better to invest into 4-10 different coins in order to avoid losing it all. Recovering 20% because one coin lost 80% is not that hard thank to your other coins. While recovering a 80% loss in 1 investment feels impossible. Also when you have many coins, if one drops and another rise, it balance your panic with joy, preventing you from doing rash decisions that you might regreat later.
4) Don't buy a coin you don't understand. If you go in any coin chart and then access it's info tab you can check their website and read their whitepaper. In the website you might find more info about the project and if is a utility it will be connected to some kind of app or software you can use. If you try to use their software and can find a way to spend their coins to use it this means that is a utility coin. A utility coin over time increase in value because more people use the system more coins are required and they will need to buy it from the exchanges. As a result it will be the main driver to organically drive up the price over time. A good example of an utility coin is $ETH that allows you to build other coins, pay for the fees to use the system and rise investments to start your project. In case they don't have a website you can check their whitepaper and see what system they want to develop and if you think that is something original then is worth investing in with caution because is just an idea and you don't know if the developer even have enough knowledge to make it real.
5) Never sell in a loss. How warren buffet says rule number one don't lose money and rule number 2 is to not forget rule number 1. Stop losses can be seen in a heat map so if you use those you will be targeted by whales only to collect your liquidations. While selling manually in a loss is not a good idea. Mainly because losses are really hard to recover and if your coin was at a specific price in long term probably it will surpass it, if the coin has utility. Regarding the losses think this. A 10% drop require 11% to be recovered. But If the coin drops by 50% you will need to make a 100% gain to recover your loss. If the drop is 75% you need to make 200% gain to recover. While a 80% drop require a 300% gain. After 25% loss the required recovery is tok steep and there is no point in selling at that point in the hopes to recover on another coin. Plus if something dropped a lot quicly it has a high chance to make a reversal and come back to your initial price.