What's the best way to make money on NBA on long term?

The information available on Basketball means that there's no easy route to success.

Have a great understanding of as many teams as you can and use knowledge and experience is about the only way.

Betting underdogs at home is probably the least bad "random" way, but it won't come out a winner.

the opportunities in NBA all seem to me to be in play.

as lori says, like most sports in the US, it's saturated in stats, and the prices on here are derived from the vegas books' point spreads, which I'd say are pretty accurate pre-game.

There's a guy with a fairly popular blog who has always backed whichever team last trailed by 20 points or so and ended up winning.

Or if they didn't win, he laid them back much higher of course.

It sounds very easy.

I used to feel NHL, a sport I grew up with, was the toughest involving a small hard rubber disc that travels at over 100 mph and bounces around erratically. 

NBA involves a bouncing ball being thrown through a hoop, bets often settled in the last two minutes.

I also think there isn't alot of value when strong teams face medium teams.   

The only angle I could think of taking is playing the match odds placing an in-running bet around 20 to 30 % above the pre-match.

IMO, in-play is the only way that you can consistently win on the NBA. The market overreacts to leads, seemingly forgetting repeatedly that basketball is a game of momentum and that a (for example) ten point lead is not that much - and it's certainly not that much in the first half. Look for these overreactions and you can do very well.

cpfc4me, agree with your 'overreaction' of the markets.  When I first jumped on board betfair, I was astonished to see the odds shift for even a 3 pt/ 4 pt lead on basketball, a 7 pt ht lead in NFL, 2 runs after 4 innings in baseball...   

I realized it was the UK punter comparing it to a 2 goal lead in football

It took around five years for the UK players to figure it out

Agree that in-running is the way to go but..

Of those options listed probably the best would be, back the big odds, that would probably do the least 'damage'

Try looking at the schedules, you can get nice prices on fresh bad  teams against tired good teams.
Teams with a big game in the next day or two will often put in a lucklustre effort in the game before.
All this stuff will be built in the prices anyway to a degree.

Move to Canada and get the dyson out is the best way