Try the singing do re mi like 10 times but in diff octaves every time you sing it:) or the lalala thingy xDy
if ur trying to sing a high part and u know u can sing but it just wont come out right
try singing it over and over (only the high part) and do the diaphragm thing like u said and breathe really deep

last thing is try dog panthing like 30 seconds u know when a dog is really thirst and u have ur tounge out and yup thats about it.

1. Know thy voice.

Spend quality alone time with your voice. Take your voice out on dates, so to speak, and really get to know it. You might even try recording your singing voice to hear it more objectively. Find out the answers to these questions:

Is my singing voice big or small? Thin or full?
What kind of vibrato do I have? Fast, slow, medium, heavy, thin, non-existent? Am I able to sing both with and without vibrato? When I sing without vibrato, does it feel different in my body than when I do sing with vibrato?

What is my full vocal range? What range am I most comfortable singing in?
Where is my passaggio (the pitch(es) where the voice changes registers)?
How long can I sing without taking a breath? (i.e. How well do I support my breath?) What do I notice in my body and what do I notice about my tone when I start to run out of breath?

How does it feel in my body when I am singing well and when I am not singing well?
What kinds of food and drink affect my voice negatively/positively?
How long does it take for my voice to "warm up"?

There are no right or wrong answers to these questions—everybody's voice is different. The more informed you are about your own voice, the better you will be able to care for it and improve it.

2. Take care of yourself.

Your body is your instrument and you only get one. So, stay hydrated. Get enough sleep. Don't smoke.

3. Support your breath.

You've probably heard this before by every choral director and voice teacher you've ever had—and there's a reason for that. Proper breath support is imperative if you want your tone to sound the best it can. Unfortunately, it seems like every pedagogue has a different way of explaining breath support, which leads to a lot of confusion. This is an area where a personal voice teacher will come in handy for you. He or she will work one-on-one with you to help you learn or improve your breath support so that your tone is always supported. [Read: "Choral Cliché: Support the Tone."]

4. Keep your jaw loose.

A tense jaw will cause your tone to sound constricted and may even cause you to sing out of tune. So, reduce your jaw movement to only what is necessary and don't chew on your vowels. For example, if you are singing a major scale on "ah," there is little need to move your jaw while ascending from pitch to pitch. Keep your jaw as stationary and as loose as possible, and think of making the shape of the vowel inside your mouth rather than with the muscles in your lips.

5. Read ahead of the beat.

When reading music, always have your eye at least one or two beats ahead—that way you can anticipate what's coming next and you'll be less likely to be caught off guard when you encounter a curveball interval jump. This can be especially helpful when doing a cold sightread through a new piece of music.

6. Listen louder than you sing.

Aural multi-tasking—the ability to listen to yourself while simultaneously listening to other singers and musicians in your ensemble—is a challenge that every choral singer faces. Please: Do not plug up one earlobe to be able to hear yourself better. Why? If you have to do that to hear yourself, then you aren't training yourself to listen holistically.

If you're having trouble hearing yourself in the group, one trick is to angle your music book or folder in front of you (but without completely burying yourself behind it, of course) so that some of your sound bounces back to you as you sing. Use acoustics to your advantage.

One of the best ways to build a stronger voice is to sing while you run or walk. Always warm up with some exercises in a comfortable key for your range. Probably would be a good idea to find your range as well. Use a piano and go up and down the scale. The most important thing with singing is to be in key with whatever musical accompaniment your singing over. Be aware of when key changes occur. Practice is essential and breathing techniques a must. Heres a link. Http://www.youtube.com/watch?v=PCpKOMyzx…