Tips for better singing:
* Stand up straight. Chest out, back straight, shoulders back.
* Open your mouth and project your sound out.
* Put passion into your singing. Feel what you are saying / singing.
* Besides vocal and breathing exercises, stretch before you sing.
* Use your piano skills (for me, my instructor suggested using online simulators since I don't own my own piano to work with) to practice matching pitches. You play the note and then sing that note back. It really helps you get better at preforming unfamiliar pitches.
* Practice. Never neglect practice or try to find an "easy quick fix" to getting good or better at singing. Nothing worth having will or should come that easily.

As for the song, be sure to talk to everyone in your group and make sure everyone can at least tolerate the song chosen for your preformance.
I'm not really into music in the same genre as JB or One Direction, so I can't help a ton, but here's a few I can think of that might help (I tried to think mostly of pop stuff since that's what you mentioned, but I threw in a few rock songs you might consider checking out):

* Skyscraper – Demi Lovato (this one is softer, with I still felt I should list it because it's a very beautiful song that would suit either / both a soprano and/or an alto)
* Fighter – Christina Aguilera
* Stand in the Rain – Superchic[k]
* Whispers in the Dark – Skillet
* Welcome to the Show – Britt Nicole
* If I Had You – Adam Lambert
* Declaration – David Cook
* That's What You Get – Paramore
* Crushcrushcrush – Paramore
* Lights – Ellie Goulding

I wish you the best of luck. If you really, really care about this and want this with everything you've got and are willing to truly work hard for it, I am sure that you guys will make it when the time comes. <3 Good luck. 🙂

Yes, practicing singing will enable you to sing better and to sing more notes. You can also consider voice lessons as well. Singers' voices will change and decline when they're in their mid- to late-50's.

Learning how to sing without voice lessons takes time and dedication, but it's not too difficult. All you need is patience and perseverance, and a room where you feel comfortable singing without censure from others. With a little self-discipline and some practice, most people can learn to sing without lessons. Clarity, proper breathing and enunciation will become a breeze–which is fortunate, as they are key elements to learning how to sing. Those things, along with developing your "ear,"–that is, your sensitivity to, and ability to reproduce, different musical tones–will set you on your way to singing in no time.

Enunciate your words clearly so that what you sing is understandable. For this, you need practice. First, find a page in a book to read aloud. Watch your mouth move in a mirror. Read as you normally would at first, but as you continue down the page, start reading more slowly. Pay close attention to each syllable as you enunciate it. Pay close attention to the way your mouth moves as you slowly and clearly enunciate your words.

Once you have read aloud to yourself, watch yourself in the mirror as you say tongue twisters, clearly enunciating every syllable:

(1) Peter Piper picked a peck of pickled peppers.

2) Black socks, they never get dirty, the longer you wear them the stronger they get. Some day, I think I shall launder them, something keeps telling me don't do it yet. Not yet. Not yet.

3) She sells seashells at the seashore.

Harsh consonant sounds while enunciating, such as a hissing "s" or a "t" that sounds like spitting, are common. Make sure you enunciate them anyway.

Practice actual singing in front of a mirror. The best way to start is by singing the vowels A, E, I, O and U. Each vowel needs a different mouth configuration, which will help you learn mouth control and clarity of sound.

Begin with A by opening your mouth and pulling back the sides of your mouth into what might feel like a grimace. Sing "A" for five counts; then close your mouth a little more for "E." For "I," make a fist and make your mouth approximately the size of your fist, a little less of a smile, but wider than A and E. For "O," make a perfect "O" shape with your mouth, and for "U," pucker your lips as you sing.

Breathe when you sing. Most people have learned to breathe shallowly, but if you want to learn to sing, you must learn to support your sound with deep belly breaths. To learn how to breathe, place your hands on your belly and inhale through your nose. Imagine breathing deeply into your stomach. Feel it rise. This is how you should breathe when singing. Practice inhaling for five counts and exhaling for five counts.

Develop your ear, or ability to retain and accurately reproduce music or notes that you have heard, by playing a random note on a piano or electronic keyboard, waiting about 3 seconds, then reproducing the note with your voice. Check for accuracy by replaying the note as you're singing it. Try this exercise with random notes that you can easily sing without straining your voice.

Sing a song now that you have enunciation and breathing down. Pop in your favorite CD or tape that you want to sing to, and listen to it a few times to familiarize yourself with the words, tonality and harmony/melody of the song. When you feel comfortable enough, belt it out. Remember, practice makes perfect, so practice the steps, and you'll soon be singing with aplomb.

You probably are straining your voice. If you really want to improve your singing and learn techniques to avoid vocal damage, you need to find a voice teacher and take lessons. There are teachers than can work with people who prefer pop to classical songs.

However, "good to sing" and "not too hard" are relative. I do have a couple of tips for you.

For one, some karaoke hosts are better than others at mixing the sound for their singers. If you have someone who really cranks up the background music to the point that you have to practically scream over it to be heard, then maybe you need to find another show if you can't ask them politely if they could make sure that the music is turned down a bit (or that your microphone and voice be turned UP).

Make sure you hold the microphone very close to your lips since most karaoke microphones pick up sound better this way. Let the KJ adjust the sound–that's his or her job to try to make the customers sound as good as possible. Do NOT wrap your hand around the actual microphone part. There is a handle. Use it. (Also as cool as it looks, do NOT swing the cord around if there is a cord. It won't help pick up the sound and it just ends up pulling the wires out of an expensive piece of equipment. If you ever saw a bunch of karaoke mikes with tape on them, that's why)

Pick other songs by the same singers as songs you know you can sing. Most of Taylor Swift's songs (especially her early ones) will be in about the same range and style as "Tim McGraw". Madonna has a lot of songs that you may also like to try out. "Like a Prayer" might be one you could try that is similar to "La Isla Bonita". You may feel more comfortable with songs in a low to medium voice range.Most of Taylor Swift's songs are a lot lower in pitch than people realize. She has a young voice so it sounds higher than it really is. Pick other songs by young singers who DON'T belt. A lot of these singers are straining as much as you probably do, if not more, but have advantage of state-of-the-art recording equipment and music producers and sound technicians to fix a lot of things. That's why so many of them lip-sync in "live" stage performances.

But I digress. Try these suggestions. Don't push. In fact, sing SOFTER if you feel you are having to push your voice to be heard. That forces the person at the controls to turn up your microphone.

Remember what you hear on original recordings is the result of many hours of work by many people besides the singer. Don't think you need to sound EXACTLY like the singer.

Plus most professional karaoke equipment have key changers. You can have the KJ move the pitch up or down to suit your own voice. Even as much as a half step can make a BIG difference on whether you strain to sing, but most listeners won't even notice the difference.