All the above advice is great. Most of it is focused on the initial high school recruiting. My advice is to also be aware that there is a good chance that you will need to make some adjustments AFTER making that victory post on Twitter and signing NLI.
The first important mindset adjustment is to realize that being committed is just the first step of the long journey through the college baseball experience. If you don't keep getting better every day, you get passed up by those who are.
Second realization is that even it you make an informed decision and choose a program with a good fit, there is still a good chance you will need to make adjustments after arriving on campus. Most high school recruits will not realize how likely it is that a transfer will be necessary, and most do not realize how small the baseball world really is. It is vital to build a good social network of all the coaches, scouts, mentors, and players you meet along the way. Do not burn any bridges, and stay in touch with everyone you meet. You never know when that 2nd baseman from your summer team 4 years ago, or that assistant coach you talked to at the showcase, or the coach who recruited you from another school, will be able to open doors for you somewhere down the road.
If you keep working hard and continue developing relationships, you will be better positioned to deal with any hiccups in the master plan.