At the high major level you'll see most recruits arrive on campus not too long after they graduate from high school. Summer school has different sessions and it depends on when you graduate when you can get on campus. The longer you are there, the more comfortable you will be with how things work.
It's a different world and the coaches that were extremely nice to you during the recruiting process don't seem to be the same person that recruited you. Why? Coaches are trying to push your buttons and see what exactly pushes you to get better. It isn't all fun and games. The strength coach will test your physical and mental limits and force you to become a better athlete. Be honest with coaches and trainers. You'll deal with soreness and being uncomfortable more than you've ever experienced. You'll have to get through things mentally that you never imagined that you'd have to.
There are some mid-major schools that get their guys on campus during the summer but it isn't quite as prominent as it is at the high major level. The mid-major level all the the way to D3, players are arriving once school starts. There are different rules at each level that I'll talk about what players need to do.
D1 and D2 programs are all allowed to have workouts with their players during the fall. The workouts can consist of eight total hours (two on floor and six in weight room) during each "preseason" week. During this time, players HAVE to soak in a lot of information. Each program is different but some will "babysit" you in those first couple of months and others will let you figure it out.
The biggest thing for everyone is to listen to your coaches. They might be doing a bunch of things completely different than you did in high school. The language will be different and you'll have to get use to it quickly if you want to contribute right away. Kelly Oubre and Cliff Alexander from Kansas saw this firsthand this year. Bill Self said they weren't ready to contribute because they didn't understand what it took to play at that level.
Another thing to keep in mind at the D1 and D2 level is that coaches can only work with their players for a total of 20 hours per week during the season. That is supposed to include practice, games, weight training, and film sessions. Games are supposed to count as three hours (that was the rule when I was at WVU). Shoot-a-arounds also counted as an hour, regardless of how long they actually were. Athletes are also forced to take one day off during the week. So, coaches are supposed to figure out how to get 20 hours of work into six days. Not easy considering all the things that the athletes need to do in order to reach their potential.
At the D3 level, coaches can't be in the gym with the players until October 15. What that means, you are on your own until practice officially starts. Yes, coaches will set up times to have open gym but they can't watch (although most figure out ways to watch a little bit here or there). Coaches then have one month to "mold" freshmen or newcomers to get what they are looking for before games begin. Most programs will have "voluntary" workouts in the weight room as well. There is nothing voluntary about them. Especially as a freshman, if you aren't in the weight room, you will lag behind.
At the D3 level, there are no rules as far as time used during the week. So, coaches could have you for 30-40 hours a week if they really wanted to. Athletes at D3 are also mandated to have a day off during the week but there is no limitation on how many hours coaches can work with players.
Regardless of how many hours coaches can work with you, you have to being willing to work on your game on your own. Most colleges will give their athletes a little preference to getting into the gym at weird hours, so make sure you get in the gym or the weight room on your own. Many colleges have a shooting gun as well. The shooting machine should become your boyfriend or girlfriend. If there is one thing that can get you on the floor, shooting is definitely one of them.
Last thing to keep in mind when getting onto a college campus is that you are a freshman. What that means is that you are on the lowest part of the totem pole. Things will not come easy like they did in high school or AAU. Playing time is determined by a lot of things and none of those include your accolades from high school.
Freshmen don't play unless they are better than upperclassmen. Freshmen have a steep learning curve. Freshmen are 18 or 19 years old, upperclassmen are 21 or 22 years old. There is a big physical difference. One thing players and parents don't want to hear is this. How many incoming freshmen started and/or played significant varsity minutes as a freshman in high school? Not many, so what makes people think a freshmen can come in right away to compete and thrive against guys or girls four or fives years older than them?
Things aren't always fun for people that don't play. Most incoming freshmen have played significant minutes since they can remember, so when they don't play they decide to transfer to decide to quit. Playing college basketball mirrors life. There will be ups and downs. Hopefully, the downs make you appreciate the ups way more.