It is very important to establish this as a bedtime routine, just like bath, songs etc. And read to them every single night. It is the way to get them reading themselves. I buy books in charity shops, and we go to the library all the time, to stop me getting bored. Always read to them something slightly more challenging that what they would read or look at themselves. My six year old is now on 'chapter books' which he couldn't read but enjoys listening to.
Mummy "Would you like a bed time story?"
Child "Yes, please"
Mummy "Which story shall we have tonight?"
Child " xxxxxxxxxxxxxxxxxx"
OR
Mummy "Would you like a bed time story?"
Child "No"
Mummy "Ok then. Maybe tomorrow"
Reading should be enjoyable and not a chore, so if you child doesn't want a story some nights, then fine, have a chat about the day instead.
Try setting up a star chart system, give your child a star or a sticker on a chart each time they sit and listen to their bedtime story. When they have got 10 stars give a little present (pack of choc buttons or something like that). After a while you could then up the number of stars required for a present before eventually weaning them off the star chart altogether, when they're a bit bigger, as they like to think of themselves! Don't get upset if they do not achieve a star every night, the child will realise that not sitting quietly will achieve no stars and no reward.
Make them a part of it! Ask them what book they would like (even if you've read it a million times, keep reading it if they want it) and let them read the characters dialogue!
I agree with above, try speaking in different voices for each character. I use deep voices for things like giants or something in the story. Do actions. Another easier way, buy the story tapes what come with the book, that way play the tape, as it reads it out loud, the child is reading the book, and will recognise the words abit easier. Another easier way is do little games etc. I bought my friends child a blackboard and hung it in his room, when I read the story to him and his sister, I always ask questions in between like who can spell (word)...or why did rapunzel let down her hair etc..
I find with my younger brother that the best thing is to fully involve the child in the book, let them touch the pages and react, ask them questions ('where's the mouse?' etc.) Also it's important to be patient and go through the story at the childs pace no matter how slow they want to go through the book also varying the tone of voice for each charecter is massive help because it entertains the child (my little brother often ends up hysterically laughing at my interpretation of the gruffalo's voice!) Also I always sit the child on my lap i find it seems to have a calming effect just to sit quietly and focus completely on the book, make it interesting enough and the child won't get bored. Hope this helps.