NBA teams are prohibited from announcing publicly the terms of any potential trade prior to its official completion via a trade conference call with the League Office. This rule applies throughout the year, including on the night of the NBA Draft.

On Draft night, trades will only be announced by the NBA during the Draft telecast, provided the trade call is completed prior to the end of the Draft. If a trade call is completed after the Draft has concluded, the terms of the trade will subsequently be announced by the teams, as per the usual rule, at a time agreed upon by all teams involved in the trade.

NBA Teams are prohibited from publicly disclosing the player(s) they intend to select in the Draft. All such selections will be announced by the NBA during the Draft telecast.

Teams are allowed to trade future draft picks (first and second round) as they would current players. However, NBA teams are restricted from trading away future first-round draft picks in consecutive years.

Source: Wikipedia, NBA.com