Throughout the history of the NBA draft there as been countless busts, and stars taken in the draft. Some stars have been taken as late as the late second round, whereas some busts, have been taken with the very first pick of the draft. Teams spend countless dollars on scouting, but still manage to miss out on talent, by either picking the wrong players or passing up the right ones. Even players like Ben Wallace, Wesley Matthews, and Udonis Haslem were passed up by nearly every team and became undrafted - only to have successful NBA careers. If all this money is spent on scouting by every team and this still happens, the question is why? Fans themselves seem to have a better idea of who to draft for "their" team than the team does. With all the information scouts have, wouldn't it seem that there would be be way less draft busts and better choices taken by NBA teams?
There are several things that scouts would evaluate a player by in no order.
1. Quantitative production: this is all the measurable stats that can be evaluated - such as points per game, assists, rebounds, etc. This can be a good indicator of how a player will do in the NBA, but does not prove that the player will do well in the NBA. A good example of a Productive College player who never could succeed at the NBA level is Adam Morrison. Taken as the 3rd overal pick in 2006, he is now completely out of the NBA despite his high level of production at Gonzaga University.
2. Qualitative production: this is much more of descriptive data that cannot nessesarily be measured in numbers. This is answering the question of how a player is producing. This is answering questions of how he gets his points (off the dribble vs catch and shoot). How he looks while playing (uncoordinated, etc.). Does he rely on his athleticism, height, or IQ to get his production. Typically scouts are more high on athetic players and those who can create their own shot than players who are strictly catch and shoot players, or players that are less athletic, even if they have the same level of qualitative production.
3. Level of competition: until recently almost all teams would never draft any players from small, low competition level schools. With players like Norris Cole and Kenneth Faried making a successful jump to the NBA, and Damian Lillard slated to be a lottery pick teams are putting this as a lower level priority when scouting players. It still does have a large effect on how high a player is taken. Many players are continually discounted because they play against weaker competition, which drops them in the draft - only to become better than many players drafted ahead of him (i.e. George Hill). Many scouts are split on just how the level of competition overseas compares to college, but it should be noted that foreign players may be even more difficult to scout as a result, often resulting in them being drafted lower than their production in the NBA dictates (i.e. Marc Gasol, Serge Ibaka).
4. Age/experience: This has been of some controversy since the New CBA as many people would rather see players stay in college longer, which was unchanged in the New CBA. Many teams value age differently as you can see it one of two ways. 1) "this player is only 18, which means he has room to develop". (or) 2) this player is 18 years old, meaning he is much to young to play in a grown mans game and is too immature to succeed as a result. Now there is some truth to both statements, but are too big of generalizations to make concerning all incoming basketball players. As the case currently most college players who are drafted right after their freshmen year are actually drafted higher than those who are not, usually this is because they are just better basketball players, not just because they are young. However older players many times drop in the draft because teams feel like the player has no more room to develop. This is the case with Wesley Matthews as he was 23 years old at the time of the draft, which many scouts feel is a negative.
5. Potential: this is mostly based on sheer athleticism, and age. A player with injuries in the past also may have "potential" to be better over time. A good example of pure potential and little production is Andre Drummond. From looking at his stats alone you would think that would be a borderline second round pick, but his sheer size and athleticism for a big man is so rare and he is so young that many teams see him as the potential to be something great.
6. Intangibles: this really includes all the hidden aspects of a player that is not necessarily visible on the court all the time. This includes the character of a player from interviews. Leadership qualities. Family babasketball history. High Academic qualities, and awards/titles would also fit into this realm. The character of a player would fit under this as well. Many of these intangibles are not well known to the public, but it is something teams find out through interviews and workouts.
7. Durability: A player who is often injured throughout his college year will definitely hurt his position in the draft. Many times teams will take a risk often assuming that a player will be able to overcome injuries to become a star. Other players draft position will drop dramatically due to chronic injuries, like Blair from the Spurs.
With all of these variables you can see just how hard it can be to pick the best player at any given pick in the draft. Players who have been extremely productive in college does not garantee the same level of production in the NBA, just as the lack of production does not necesarily mean the same thing in the NBA. This is why it is so important to look at every single one of these areas in a player and not get hung up on one specific area of a players game. The Blazers went away from this model in the Jail Blazer era, disregarding the lack of character in a player for production. This is why it is so important to have an excellent scouting department as it will reap dividends in the end. All of these areas should be taken into account in comparison with the needs and culture your team has in order to make sure the player you draft will fit into your teams goals over time.