when do i use はand わ
i know that in the japanese language a lot of words use は instead of わ like こんにちは and こんばんは, i also think the particle わ is written as は also. i was curious as to if there was a way of identifying when to use は in the place of わ?

Question

when do i use はand わ
i know that in the japanese language a lot of words use は instead of わ like こ んにちは and こんばんは, i also think the particle わ is written as は also. i was curious as to if there was a way of identifying when to use  は in the place of わ?

Answer

when は is read as ''wa'', it's a particle that is used to mark the topic of sentence, in other words "the topic is anything that the speaker wants to talk about''. 
when は is read as ''ha'' is just the hiragana that is part of a word as in: 箸 HAshi = chopstick,  橋 haSHI = bridge, 花 haNA = flower...
now for こんばんは，こんにちは は have a look here: http://japanese.about.com/od/simplejapanesephrases/p/sjp14-3.htm

I hope it helps you a bit.