Also there are free bet prediction sites that you can use for it. I remember in the past about a free prediction site that is good in predicting under 2.5. After checking the site, I will check more information about the league and the clubs that are playing before betting in it. Paid sites are scam.
Except there's match-fixing, everything any paid site does is guess work like free sites give out. Everything in picking odds is pure luck. No one can of certainty tell the future. I remember when as a youngster we used to buy "keys" to NAP or do permutations of football matches every Friday as against Saturday in local pool offices. In most cases (8 out of 10), those keys bought weren't winning numbers. For those who don't know what "keys" are, they're supposed winning numbers of matches yet to be played but concealed. Those who sold them claimed they bought them from bookies. It was all a marketing strategy.
As for how I decide my bets, I just go with my gut feeling. I don't like analysing stuff because there's no end to what we analyze of things that depend on luck for result.