As a professional musician, here's some tips I've picked up from a variety of singers:
When you are speaking a lot (like when teaching), try to vary the pitch of your voice a bit. Speaking constantly in the usual, low, monotone range of your voice is very hard on the vocal chords.
Keep drinking water, including before you go to sleep. When you are becoming dehydrated, one of the first places your body pulls water from is your throat.
Drink warm tea mixed with honey.
I realize this one may not be fun while you're at a karaoke bar: but try not to drink anything cold after your voice is warmed up. It's like pouring ice water on a hot engine. If you can live without beer, go for room-temperature water.
Swimming is the best exercise for singing.
When you are singing, try not to sing from your throat, especially on the high notes. Most people breathe high in their chest and sing from their throat. If you aren't familiar with breathing low in your body or singing with head resonance, you're doing extra work and straining your vocal chords. A voice teacher could help with this.
Go to a music store or online and find "Entertainer's Secret." It's a throat spray that some singers I've known swear by.
I hope some of this helps. Good luck!
