There are several ways.
The first is to refer other friends/family members to join before you actually go to boot camp.
The second is to have SOME college done. If you have enough credits, you may not qualify to be an officer, but those credits do count towards promotion in the enlisted side.
The third way is to prove yourself worthy during boot camp and become a squad leader for your platoon. Every squad leader in my platoon got meritorious PFC.
As far as Honor grad goes, there is only one out of about 1000 recruits that you will graduate with. He will be the Guide(leader) of the platoon that is chosen Honor platoon. That is based on how your platoon does on various scored events throughout the entire 3 months. If you are the guide and already rated PFC, you can actually be promoted to LCpl out of boot camp, although as i said, its quite rare.