I don't use kanji flash cards at all. I never could learn anything from them.
I use the same books as Japanese kids. Each lesson is divided in two. In the first part there's 7 kanji, one or two of their readings (others come later), stroke order, example sentence and additional vocabulary. First I translate the lot, then write the kanji 20 times each (no problem with stroke order after that, I can tell you that!). Then I read out loud the example sentences. Then I memorize the vocabulary again.
In the second part there are lots of example sentences written in kana. I write them with all the kanji from this and previous lessons. The most important thing is to drag the new info from the brain at whatever cost, without peeking. It only needs to be done once.
The whole thing takes about 30-45 minutes, but I only do it every other day. The other days I practice the last three lessons, reading out loud and air writing. By learning in Jouyou order I can keep track of my level and immediately know whether I'm supposed to know a particular kanji yet or did I simply forgot it.
My method is not so hot for flash card type of tests, but I also have a pile of kanji reading books, which are stories written with certain level of kanji (no furigana). I can read them just fine. I base my learning method on the fact that as long as one can read full Japanese text with understanding, one doesn't have to spend extra time on vocabulary or grammar. Of course I do have grammatical reference books and a nice electronic dictionary. Three, actually, but I only use one. I had some paper ones too, but I burned them dancing around naked and laughing maniacally.
To look up kanji with them is cruel. Beyond cruel. Übercruel.
One extra plus point about the kanji learning books is that they are very often written in regional dialects, and going through them really helps to filter them out. There are some weird wordings out there!
And I concur, the most difficult kanji to learn is indeed, the first one!