1. Do not be in haste. That is the reason people think of day trading and lose
Before making a trade always make a plan what are you gonna do with your trade, analyze the market, check the recent market situation and trend before making an entry. Try to have a confirmation.
2. Having it in mind that it is better to earn little than to lose big all because you want to earn big
Profit is profit at the end of the day, others have a goal there's a number of profit they can get and lose per day so they didn't carried away too much with the market stand this helps you at the same time control yourself. At the end of the day your accumulated profit are your goal.
3. Average instead of martingale. An example of this is if you have $1000 for trading, you can begin with $200 and always be satisfied with the profit. But it you are losing, you can add $200 to it and so on to help you increase the chance of making money as it will make the market price get near to the price you bought the coin.
I personally not recommend this because you are way making too much risk with your asset. Still consider having a risk management. Like what you've said in no.1
4. Be careful of altcoins. Although I trade altcoins but I use very lower amount of money for it. They are very dangerous.
Not all altcoins are bad just make sure you know how the project works and what are their future plans such has having a documentation and roadmaps to make sure you have keep intact and can exit if its already skeptical.