Japanese has a completely different system of writing than English. In Japanese, there are no letters that represent one sound, but characters that represent syllables (with the exceptions of the vowels and n used at the end of some words). Vowels: a, e, i, o, and u all have their own characters in all scripts. The vowels are read and pronounced similarly to the way they are in Spanish (a as in father, e as in bed, i as in stomping, o as in oval, and u as in huge). The other characters/syllables are formed by adding consonants in front of the vowels. Ch and Sh sounds stay together and additionally combine with vowels. There are no separate s, c and h to use. Try breaking down basic Japanese words (uchi, kodomo, amerikajin etc.) into syllables and you will begin to see how it all works. You will probably also begin to predict how many characters will be in each word, at least in the first two writing systems: hiragana and katakana.
Hiragana is a beautiful script. All 46 characters in hiragana have flowing lines, like cursive. It is used for words of Japanese origin and makes up the bulk of most writing in a sentence. The following is an example of a sentence written completely in hiragana: にほんごがすきです. (Nihongo ga suki desu). It means "I like Japanese." Notice there are no spaces between words. You will need to practice reading the same sentences over and over again to get used to where words begin and end without getting confused.
Katakana is the Japanese script that is typically used for foreign origin words or to create emphasis. Like hiragana, there are 46 characters. They represent the same syllables; thus the intention and origin of the word being read or written must be taken into consideration. ニホンゴガスキデス (Nihongo ga suki desu.) This means "I like Japanese." This sentence would not normally be written only in hiragana or only in katakana.
Kanji are characters of Chinese origin that contain many more strokes than hiragana or katakana. They can be read using several different syllables. They tend to derive their meanings from images, which may be impossible for those unfamiliar with the cultural context or reference to decipher. There are at least two ways to pronounce each kanji. They are usually read differently when they stand alone and when they are combined with other characters to form a more complex word. For example, 高 can be read as taka(i) meaning tall or high, or ko as in 高gakusei (kogakusei) or high school student. Although there are thousands of these characters in Chinese, the Japanese regularly use about 2,000. There are few easy ways to learn kanji, and all ways require study and memorization. As you learn more of them you will notice that the plentiful lines begin to make more sense to you. You will notice that many complicated kanji are made up of parts of simpler kanji that you already know. This will help. Reading and practicing elementary texts will help you too.
After memorizing hiragana, katakana and some basic kanji, try mixing them together by reading some books at the elementary level, or try reading manga. Here is what our sample sentence would normally look like. 日本語が好きです。It is still read 'Nihongo ga suki desu' meaning "I like Japanese." Practice inserting the kanji you know into words and sentences that are mostly hiragana or katakana. Slowly you will recognize them more easily and be able to read them without thinking. Practice makes perfect.
If you want to practice, get the program NJ Star. With this program you will be able to practice typing in all three systems interchangeably. What's best about this technique is that when you type in a syllable which has kanji, it will give you several to choose from to make sure you can use the kanji you don't have memorized quite yet. It also has a dictionary feature. Read what you write. These two skills go hand in hand. Not learning one will keep you from progressing faster in the other. Good luck and great reading!