Let's say a player is drafted in the 2012 draft. What is the intermediate process for him getting a call to the Major League team that drafted him?
The exact path is very different for each player. Many players will skip one or several of the following levels of the minor leagues.
For college pitchers, often the first thing they must do is finish their current collegiate seasons.
Here are the possible levels of professional baseball in most major league organizations:
Extended Spring Training - A short season league with very lax rules where players can work on things and get extra reps before either being assigned to a minor league team, or get some work before taking a break before fall baseball).
Short Season A ball- Often the first stop for prospects, this is usually a short season league that plays part of the summer. Gets kids ready to play professional baseball with a season that is only slightly longer than the typical college season.
Fall ball - Played in Arizona, the fall league is where a lot of guys in the minors go after either a short season and some rest, or after a full minor league season.
Low A ball - Often the first stop for a new professional ball player. This is where they get to cut their teeth and face other professionals for the first time.
High A ball - Advanced players will sometimes start here, but it's often the second half of year one, or year two for players who do all right.
Double A - It's rare for a player to start at double A and most players here have been in their club's system for a year or two. There are some veterans around who have been playing minor league ball for a few years and likely aren't going to make it past this level.
Triple A - This level is a mix of young guys who are close to the big leagues, old guys looking for new life and the so called AAAA players, guys who might get a short callup but are likely to spend the rest of their careers bouncing around AAA farm clubs.
Winter League ball - This is a place where guys can get extra work. It's most often played in Latin America and the Caribbean Isles where it's warm enough in the off season to still play. Guys will head down if they need extra work, just love playing and can't get enough, or for any other reason. These are the professional leagues in these countries so they are filled with guys who either were discovered too late to come to the US and play in the big leagues, or who weren't quite good enough to get signed. MLB players who come here will often only play in a handful of games, just whatever they need to get the extra work they require
Big Leagues - This is the end goal, what players often work between 2 and 5 years to get to. Once they are here they finally start making the money they dreamed of and can play baseball at the highest level.
It's a long road to get from the draft to the major leagues, excellent players often shortcut one or many levels of their team's farm system, but most players play for at least part of one season in the minor leagues (the last player to go straight to the bigs from the draft was Mike Leake in Cincinnati a couple of years ago)