1: personal strategy is to gradually buy into BTC or an 'established' altcoin although sharp peaks are avoided. A value going down yields the oppertunity to buy in more. I avoid using this strategy with random altcoins as the chances are high money is being thrown at a dead coin.

2: A short-term strategy I can think of is buying into a coin that's falling like a rock, as an 'upwards' correction usually follows. This is risky however and I personally never do this (anymore).

3: a thing I learned is that buying into rapidly rising coins (FOMO) isn't a smart thing to do to say the least. Therefore, I've switched to the method I've mentioned at point #1!

4: that depends on your capabilities and available time regarding trading. I would probably fail miserably myself at day-trading, though others could gain massive profits this way.

5: investment!