When I was learning Hiragana (and later Katakana), I practiced one line at a time. So first do the vowel line, then the 'K' line, then the 'S' line, then the 'T' line, and so on. I found this the easiest way to learn them. Don't worry if you don't have them all 100% at first because as you start working with the language more you'll learn that some characters are used more than others (and some are rarely used at all).