I think a lot of people regret not buying coins that were cheap and instead bought coins that had already had huge pumps. My biggest regret of 2018 was just looking at the top 100 coins. I know most people don't even look past top 10.
Now, I try to monitor CoinMarketCap or CoinGecko to mainly look at big movers. Lots of small coins that have potential get noticed early on and make big moves. I try to look into these. If they moved just because the volume is $100, then I move on. If they have a good volume and are making something that could have real demand, I check it out.
Right now, I'm look at VEIL, a new privacy coin.
The coin is doing really well even though it's not on a big exchange. The driving force is that it has a good development team that's trying to solve a real problem in current privacy coins. They are making private transactions more scalable and faster by advancing Zerocoin Protocol.