Yooo man.
First off I'm going to say it's not worth it really. In most high schools nothing remains a secret. If your going to hook it up, word will get around that people got sacks off you. Especially if you sell right with good price and good product. People will ask their friends, 'Damn where did you get this shit?' and most of the time they will get an answer. Now this is okay sometimes as it gives you more customers but it's also a negative because then other people hear people talking about YOU. You'll probably meet a lot of contacts in class. Chat it up, start talking about buds, say you got some good shit, exchange numbers, hook it up after school and bam you got a regular. Because regular hookups are making you money, treat them nice, hook their sacks up a little fat and tell them, toss a free nug of your new shit to try. It's the little shit that counts, and keeps them from going to someone else. If your hooking it up good for the money, and you are reliable, and have good shit there is NO reason for your customers to go somewhere else. Not worth the risk of bad service/light sack/flakes/cops.
Now the way to do it in high school is keeping a SOLID customer base. Make a few friends, and hook them up, then go out and chill with cool experienced relaxed people and make good with them. Slowly slowly expand to sell to people. If someone from this customer base hits you up and says, "hey my friend needs a bag can you hook him up?" tell them, "You get the money fronted, and YOU pick it up from me. I'm not meeting anyone else." A lot of the times a dealer will go and hook up a 'friend of a friend' and end up getting jacked. Then you call the person who connected you to the person that jacked you, and they say, "That sucks dude I'm sorry, I don't know josh that well I met him at a party once."
Don't get in over your head, don't be making contact with a fuck tonne of people cause it's not worth it. Keep your contacts small, but if you meet the right people they should need bags pretty often.
If anyone ever hits you up and asks for a lot of buds, that's a large red flag. If they ask for some weight, and aren't ALL ABOUT THE PRICE NEGOTIATING, HUGE HUGE HUGE RED FLAG. Sometimes people will buy a few small bags to gain your trust, then ask for a large amount and say 'i just got paid' or something that's another HUGE RED FLAG, they want to jack you.
Also always do it outta school, don't get overheard talking about that shit. I never let anyone know where I lived, if I had to do it on foot I would go for a walk and walk outta my neighborhood into a different one. Also, don't arrange to bring bud to school to hook someone up with. They might be setting you up for a fall. Fuck them if that's the only time they can get it. I'm pretty sure drug charges in public/vs IN SCHOOL are way way way different. Like misdemeanor turned into felony EASY. So making contacts is fine at school, but everything else isn't.
Anything else?