Look at The Book DVD's for super detailed instruction through almost every trick you can think of, and Murray's Detention DVDs are also good. When it comes down to it, though, when trying your first invert, you just have to go for it. My first attempts were weak and I took some pretty nasty crashes, but once you start getting comfortable being inverted, you'll learn more with ease.
Also, if you have your 180's down before you start trying inverts, it will be a piece of cake adding them to some of the base inverts. Just an example, last fall I only had a hs backroll, and this year was able to learn a ts frontroll, crow, and R2R.