key indicators:

1) big % gainer trading MASSIVE volume
2) Low mkt cap + low float - ideal share structure 
3) holding vwap all day ideally
4) late day pattern - 2PM+ 
5) selling into squeeze late day or afterhours - sometimes can swing some overnight for potential gap up morning spike if didn't reach targets.
6) no overhead resistance near by 
7) low potential dilution ideally - be cautious with potential offering
8) key round levels - $1 so important level

the idea is the morning short sellers that looking for gap and crap to exit the position after the stock holding too well + momentum buyers looking for next leg up.

few examples recently on day 1's: GV, PSTV, XHLD, MLGO, CRVO, RGC