I went to night school vocal lessons. What you realise is that everyone else has the same problems, its a question of whether they have the nerve / guts to admit it.

Uncle Daves "learn the words" point is also spot on. You only start to perform a song after you've stopped worrying about it (and worrying makes you tense which is A BAD THING).

You have to warm up the voice, loosen up the head, throat and upper chest muscles, avoid alcohol and indeed anything chilled. Cold fluids tighten up the throat. Personally I fail on the beer front but you can't have everything.

Certainly the things that help most to avoid
soreness have got little to do with technique - pick your key well and never overstretch. Having said that developing your breath technique makes singing that much easier you will end up louder anyway!

Whilst on a good day with a following wind I can get to Bb and not sound like a cat, I only tend to go past F for held notes in a song if if feels wrong in a lower pitch (e.g. Eric Carmen - Hungry Eyes - sounds rubbish pitched to an F but has the right feel when I use G!) or it is so rangy that the bass end sounds awful as well. Iterestingly since I took lessons my lower register has improved hugely, which I attribute mostly to better breath control and resonance management. This takes pressure of the top end as I can now sing songs in a lower key without sounding gutless or losing pitch. An interesting practive exercise is to sing your favourite songs one octave down! Its also a good warmup exercise. I do this in the car on the way to gigs.

I use a compressor on vocals to give more gain in the quiet bits of my range and take the volume out of the louder areas (i.e. to compensate for having no microphone technique due to playing a keyboard at the same time!).
On the subject of keys, I'm sure I read that Art Garfunkle picks the key for "Bridge over Troubled Water" just before he sings it, depending on how good feels.

A bit of technical stuff which may help...

Our teacher placed great emphasis on space, relaxation and resonance. It's all connected. The space bit is that if you have your mouth constricted, or your throat is "tight", theres less of an opening for the sound to come out of and you sound more like a duck. Your throat will get tight if you aren't relaxed; if you are breathing using your chest rather than your diaphragm you are onto a loser as the act of breathing tightens the throat. You can get more space if you move you ribs out of the way - ever wondered why the serious male singer can get pigeon-chested? You can't hold the ribs out if you are using them for breathing. Shifting the ribs is beyond me, however. Heaving shoulders may emphasise a big emotional point of a song but they do nothing for the quality of the voice.

You may notice a lot of "Broadway" singers always sing to the balcony. This keeps the airway from the throat out through the mouth open and unobstructed. Singing to your feet is therefore a very bad idea!

You can alter how you sound by adjusting the shape and tensions in your face. Smiling makes you sound brighter - singing with a "depressed" shape makes you sound duller. You can experiment by humming a constant pitch and moving your mouth and face around to see what differences it makes to the tone.

The tensions in the face and throat also alter resonance, which also affects the sound. You are getting somewhere if you can hum a note with your mouth closed and get you lips to vibrate in sympathy. If it starts to tickle, all the better!

Also, singing wearing spectacles makes you sound more like a duck. I use contact lenses when signing - you really can tell the difference if I'm wearing glasses.

Hope this makes sense and helps!