What's always odd about this topic is that NBA fans seem to do more hand-wringing about tanking than any other league, but the NBA is the only league that has implemented anti-tanking policies (the lottery).
The short answer to reducing tanking incentives is to flatten the odds for the top picks and possibly draw for more than the top 3, but those in turn increase the incentives for missing the playoffs. Look at how critical people here are of our making the playoffs - imagine if we had say triple the chance of landing somewhere in the top 5 picks as we would have had for the top 3 under this system. You'd have fan bases openly calling for coaches to get fired for making the playoffs, which is even more perverse.
...the core of the problem is to me the core of a lot of the league's problems - the regular season is almost completely irrelevant. The relative ease of making the playoffs, the grind of 82 games a year, and the reductionist thinking of "only a championship means anything at all" are all components of that. But every approach that addresses that reduces revenue, so it's even more of a no-go.