modmyi
iphone dev team blog
youtube are great ways to learn.
The video's are astounding in detail but you must keep in mind that some are old and out of date and some are new - need to keep up with the news.
my daily routine of websites is to read musclenerd/comex twitter and iphone dev team - the latest news and talk seems to come from them - they are there to answer your questions when they say "itunes 10.x is not safe yet" or "wait for the beta's to settle" then you should consider their advice 1000%.
Other than the early bootloader 2G,3G, and very few 3GS - it's darn near impossible to brick the modern devices. The early models have bugs which can be exploited to say load android - you can roach the dfu restore mode if you try really hard (or on purpose).
Good rule of thumb is to wait 24-48 hours after a new JB comes out and READ THE FORUMS (modmyi, sinfuliphone, etc) to see what people are saying .