How do judges determine sentancing? cl A misdemeanor in alaska ?

a minor convicted of purchasing alcohol. How do courts decide what the sentancing is? Like online I read everything from a 10k fine, jail time, loss of licence ect ect ect. But dont they try to make it revelant to the crime? I herd for minors they normally get community service ect for a first offense? True? Im not even going to youth court im going to the regular courthouse, I am planning on pleading guilty.