Kunyomi or Onyomi kanji reading. You can't really be 100% sure, but lately I do guess right of most of the time with characters I know well. When you look them up afterwards, it helps you remember them very easily if you guessed them right. If you think about looking up a difficult English word, it's not always easy to know how to pronounce it (which parts are stressed in particular) just by reading it, so it's not just Japanese that's tricky like that. I think teaching yourself kanji like that will create a lot of headaches later down the line. A lot of difficult characters contain radicals that are characters themselves. Look at 貝 and 斤, and then 質, for example. There are a couple of textbooks that structure a kanji-learning course around this concept. It ignores how to read the characters completely, for reasons that we've explained already: the best way to learn to read... is to read.
As for the confidence issue, I'd like to meet somebody who was confident about learning kanji. Kanji Game, a free program for studying Japanese characters. Learn Hiragana, Katakana, compounds, and vocabulary. Reviewing the Kanji. Wakei] kanji pics generator. Charles Kelly's Online Japanese Language Study Materials.
Characterizer: Japanese and Chinese Reinforcement. Welcome to Kanji Practice.