From the sideburns make it go straight down (as in, not curving back towards the ear). Once you get below the jawline, bring it up from the midneck mark to a nice distance below the chin. Not too close, but not too far. I prefer sans mustache, but that’s because I’m 21. Also, I think it looks nice without any hair climbing up the chin.
I just shaved last night. Otherwise I would take a picture and make it my avatar.