As soon as possible! And as much as possible. You see, untill some stage learning words and learning kanji are two different things, but when you are approaching a more compex stage you'll need to know the kanji very much - and you'll be ready for it. And do use an SRS-system for learning - I am using Anki, the "KanjiDamage Plus" deck. The memory hints of this deck were not useful for me, I invented my own, but the arrangement oreder, in which this deck introduces the kanji, is simply brilliant.

i reccomend using a website called memrise.com,I am using it myself and I am finding it very helpful for learning kanji.

The time that most textbooks starts Kanji varies, but typically learning the Kanji starts right after finishing learning the Kana. I did have one that started at beginning of the second book, but it is better for it start shortly the kana. The best way to get fullest use for learning Kanji, is having book that introduces the Kanji as part of the text. The one book, that is app, that I like using is Human Japanese.There is also Japanese DS game that is good for learning the Kanji called Kakitori-kun, which I plan on using when I receive it.

Hey.. I am a beginner too. I've started learning Japanese only a few days back and I'm already learning simple Kanjis. I don't think its that hard so I recommend you give it a try :) I'm using the free "imiwa?" iOS app and it has kanji categorized by school grades which I find quite useful. It also has Kanji categorized according to the number of strokes (Bushu). Alternatively you can also use flash cards on ankiweb.net HTH..

Flash cards are useful. Also, some textbooks and websites actually begin introducing kanji slowly as you progress and you begin learning basic kanji very quickly. I'm not entirely sure when is the best time to start learning them. My personal advice would be to start as early as possible, but not to push too hard. Don't obsess over them, just start memorising them for words you're using often at the moment.