Here's a few tips to help you when doing your homework:

Create a homework plan

Set a time each day to start your homework. There are many sites with information on creating these plans and when you have created it make sure you stick to it. Hang it up in your bedroom so you can see what you need to do each day.

Turn off the TV

You won't be able to concentrate with it on. If you need some background noise put the radio on but not too loud!

Don't do it all at once

When doing your homework make sure you take regular breaks. A good plan is to work for 20 minutes and have a 5 minute break. Or finish a particular piece of work and have a break before starting something new.

Choose a quiet place to study

You can't work with noise and distractions around. Make sure everyone else in the house knows you are studying.

Make sure where you're working is comfortable and suitable for homework

Sitting on the sofa isn't great, but using a desk in your bedroom or a table in another part of your house where you can layout all necessary books etc will work much better.

Ask for help if you need it

But don't rely on your parents or friends to do your homework.

Ask your teacher for help

Make sure you understand what you need to do from your teacher before you leave their class, so ask questions during class if you are unsure.

Start homework at the same time each day

Get into a regular pattern with your homework. Plan on starting soon after you get home to make sure you finish it and have time to watch tv, chat to friends etc before you need to go to bed.

Reward yourself

Set yourself targets and when you achieve them give yourself a treat, such as I'll finish this piece of homework before I play on my Xbox or watch tv.

Double-check your work

Spend 5 minutes checking what you've just done.
Good Luck!