Get a mouthpiece for sparring. Start with a cheap 2 dollar boil-and-bite one (from a sports store like Big 5) like they use for football. If it's tanhe football version, it will be identical the the regular generic one except have an extra tether part that clips onto the facecage of the football helmet (snip that part off with scissors before boiling it)
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If you want to actually get useful skills and not just burn off a few pounds of fat while getting slower and stupider like most of the rest of the class, you have to get private lessons. Private lessons are not something that is talked about but it is assumed you already understand that they are necessary. They're not going to really teach you anything unless you literally pay them by the hour for instruction and to polish your technique/ movement during those sessions. Good news is, since you're paying for it, you can request to them what things/area you specifically want to work on (if you don't, they might end up having you just do random aerobic stuff while they wait out the clock [just like in regular gym class]- they'd love that)
Make sure to get private lessons from someone who is very technical. Also they should be good at explaining things (these guys often have a good or dark sense of humor).
Private lessons are part of boxing culture, but they don't talk about them or demand them because it is assumed that most boxers are too poor to afford them (and when they DO have money, they will shell out when they are able for sporadic lessons or series of lessons)
Usually, if they aren't famous, the rate is something like 20-25 dollars an hour. If they are decently good, it will be WORTH IT. If not, it will just be more wasted time and money. Be careful who you ask. Also you can often negotiate bundles for cheaper than single lessons.
It's not wrong to ask another boxer for help, but you should immediately offer to compensate them for their time/effort (with either money or lunch- because boxers are poor). You can ask for help to fix a technique of yours in exchange for buying them lunch that day, things like that. If they want more, offer more. It WILL be worth it. If they dont want to help, then go to someone or someplace else.
Scrounge good, accurate knowledge however you can. Don't ask brawlers or idiots. You want technical help, not how to learn malfunctional mistakes
Good luck!