I've got a confession to make. I've been singing for a long time (since about right after the moment I started talking), but I've only recently (in the past year or two) started singing in a way that doesn't damage my voice.
As a musician, I'm embarrassed to admit how masochistic my view of singing was. Basically, I saw singing as some sort of weird workout where I strained my voice to try and "feel the burn" (it didn't really help that I developed a penchant for "alternative" styles of music).
Through a process of trial, error, and some scattered advice, I eventually got better at hitting notes. Unfortunately, pain was still a major part of my singing "technique" till the day I had a long-overdue epiphany, and I decided to try and sing without hurting.
Here are a few lessons I've learned the hard way. Following these (kind of obvious) tips has kept me singing pain-free for the past few years.
1. Practice songs one phrase at a time.
Singing is a physical activity. Singing a song is kind of like navigating an obstacle course or executing a gymnastics routine while blind-folded; It can definitely be done well with practice, but it can also be physically damaging if you don't take your time.
2. If you know it's going to hurt, don't do it.
This is why practice time is important. If you're about to sing a note and your spidey-sense is telling you to brace for blood, don't try to sing that note. Use your practice time to workshop a strategy for each phrase. Practice notes individually if you have to.
3. Get control over your abdomen.
There are thousands of different singing techniques. There are hundreds of different (often conflicting) ideas about how singing actually works. No matter what school of thought you subscribe to, abdomen control is necessary for singing loud without straining your throat. You don't need 6-8 pack abs to sing, just enough muscle to feel and control expansion as air comes in, and contraction as air goes out.
4. Stay hydrated.
Again, singing is a physical activity. All of the other reasons to drink water for physical activities apply. Plus, imagine your vocal cords chaffing. You don't want that.
5. If it hurts, stop doing it.
Stop. Take a break. Try something else. If it still hurts, start rest and recuperation. Don't run on a broken leg and don't sing with a strained throat.