How do you predict over/unders for games???

How do you predict over/unders for games???  I have used many formulas in spreadsheets to estimate an over/under based on season to date results, last five or ten games results, away vs home score results, effective possession ratios & effective field goal percentage in basketball, etc.  I've used over/under record percentages to no avail.  I rarely hit over 50% in a week... Usually 40-47%.  What do I have to do to get some solid over/under winners?  I filter out the iffy games and pick the best looking ones, but they lose more often than not.  Please share any advice, insight, systems, methods, etc. that will produce profitable over/unders.  Line moves are cool, but only work at certain points in a season.  I'd like to find something consistent and dependable year in and year out. 

One way is to go wholesale.  Every NHL game over 6 and under 6.5.  Chase using this progression:

2.25, 5.50, 11, 16.50, 27.50, 44

Move up 1 unit after a loss and down 1 unit after a win.  The series ends after 2 wins. I will do it for a week or so at a time and it usually wins.  Also, do the same for MLB.  Over 8 and under 8.5 - no Coors Field

I should also point out that the Great DanRules24 used the system I described from I believe 2011 - 2015.  The thread is on here somewhere.  

Chasing/martingale is not my style, but thanks for the info.  Many years ago, ESPN2 games had a habit of going under.  Also, I've noticed that when two under teams meet or two over teams meet, it tends to go opposite of the o/u trend they've been on more often than not.  Streaks can be good, but one must be very selective.  I used to do a labby chase against the o/u for teams that have gone four halfs in a row...  say NC had every half go over in their last two games, then I'd do a two-half chase for the UNDER the next game.  I used to track all the halfs, but I don't have the patience or time for it anymore even though it does win at a good pace.  If I could find a site that has the 1h & 2h info and spread-o/u results without drilling into the boxscores, I'd certainly go that route.  Anyway, I hope something pops up here that is more helpful in picking a single full-game o/u. 

@Surfer2

Let me make sure im correct so nhl totals anything 5.5 goals to 6 goals bet the over, and 6.5 to 7 goals bet under ?

also are there any wholesale key numbers for basketball? thanks for the info

That is correct.  Any NHL game with a line of 6 or lower, bet the over.  Any game with a line of 6.5 or greater, bet the under.  Good Luck 

@azman1

 That's a good way to lose a lot of money