The NBA Draft is a little unique when compared to things like the MLB Draft or the NFL Draft. While the NFL has turned the combine into a pre-draft event, there's nothing quite like the NBA Draft Lottery, which has an odd and short history.
Early on in the NBA Draft's history, teams would draft in reverse order of their win-loss record, but there was a rule for special "territorial picks". This rule allowed teams to draft a player from the team's local area, but doing so would forfeit their first-round draft pick. This means that back in the day, the then Washington Bullets could have used a "territorial pick" on someone like Georgetown's Roy Hibbert.
In 1985 the NBA put in a lottery system to battle allegations of teams losing on purpose to gain the first overall draft pick. The lottery system involved a random drawing from a hopper. Inside each envelope were names of the non-playoff teams. The team whose name was drawn first would get the first pick, the second the next pick, and so on.
Unfortunately, that could shift power to some fringe teams by giving them the first overall pick and instantly making them a title contender while the worst team in the league could have the final lottery pick and left with fringe talent that wouldn't really improve their team. Think of the Washington Wizards getting Patrick Patterson instead of John Wall?
After more allegations of rigging and it not really working out, the NBA moved to a more weighted system in 1990, which gave the team with the worst record the best chance to win the first over all pick. The worst team would get a 25 percent chance to win the first overall pick with the chances decreasing for each respective team, with the 14th ranked team having a 0.5 percent chance to get the top overall pick. This didn't necessarily guarantee that the worst team would get the top overall pick, but it also created a more level playing field when it came to accusations of tanking games. Tanking no longer guaranteed you anything.
Currently, the Wizards have a 19.9 percent chance to land the top overall pick, finishing with the second worst record in the NBA. The Wizards haven't always had much luck in the lottery, or the NBA Draft itself, as Bullets Forever describes:
Since the inception of the Draft Lottery in 1985 (27 seasons ago), the Washington Wizards have missed the NBA playoffs 17 times. Over that time, the Wizards have stayed at the same position in the draft five times, moved up two times (2001 Kwame Brown, and 2010 John Wall) and moved DOWN 10 times.