1. Buy the dip - you know when to buy by watching the volume. You compare the volume to that of previous drops on a relevant timeframe. Also if there is a downwave with the same or greater volume than the previous wave and the price only goes down to greater than, equal to or slightly below the last wave.
2. Buy a breakout - a breakout is the moment when you can see on the chart that all hope for a continuing downtrend is lost. Its usually when a slightly downward sideways line is broken.
3. Buy the wall - When a massive sell order starts getting bought out I try to buy the last piece of it.
I dont have any solid strategy for selling. I'm always terrible at that and leave tons of profit on the table. I'll also usually stop out if I see the price rapidly returning back to my buy level and not playing out as expected. If I see a rally becoming weak I'll start putting stops along the trendline that I would know would be really bad if broken. That's how I got out at $18800
Yeah this is actually not bad advice. A pattern of what you mentioned does somewhat exist based on past observations. Obviously it's not the law.