Assume that you are in new place and trying to learn what is written in the city bus. Suppose it is Tamil and you never read Tamil. How you will do it? For kids, situation is similar. There should be systematic approach to handle this. For kid, an additional step is to explain her that what we speak can be written as well and what is the use of writing word.
Instead of memorizing word spelling, motive should be to generate interest on kids about spelling word. If interest is nurtured, kids in turn will learn more than what you teach.
Teach word spelling in the form of song
Pick words in kid's favorite song and help her to write down.
Avoid teaching complicated spelling at the beginning.
Ask kid what she wants to write. Be cautious not to select complicated word even if kid liked it. Her liking may disappear after witnessing complexity.
Picture words - Words like jump, walk, and eat are good for doodling with. Ask your child to draw in and around the words to make them look like what they're saying. Some letters can jump out of jump, walk can have a pair of feet added to the bottom of the k; and eat can be put on a plate.
https://www.youtube.com/watch?v=ELHOPldO_qg
http://www.dummies.com/how-to/content/teaching-kids-to-spell-sight-words.html