Where are you studying? What’s “out there” completely depends on your environment. I read that in Mainland China, traditional characters are making a comeback, so that over a half of university signs and about 80 pecent of restaurant signs use traditional characters. These numbers are even higher in southern cities like Xiamen.
Can’t say that there’s a systematic way to study the relationship of traditional and simplified characters. Mainland Chinese can read traditional because they see it more and more in everyday life, and because the historic (pre-1950’s) texts are written that way. It’s more surprising that most of my Taiwanese friends can read simplified (although they will claim then cannot write it). I guess this is also a process of natural assimilation, from movies, books etc.
So I think you have to sort of pick it up yourself. Good dictionaries to use are the Oxford Consise 2nd Edition, and the Harbaugh Zhongwen Zipu (zhongwen.com) , they both contain trad. and simp. side by side.
As for the relationships between simp. and trad., they fall into several categories:
- Replacement of a complicated phonetic w/ a simpler one, ex: deng1 燈 becomes 灯, or guo2 國 becomes 囯
- Eliminating part of the word, ex: mian4 麵 becomes 面
- Adopting a shorthand convention already used in handwriting, ex: 個 becomes 个, 見 becomes 见.
One of the failures of simplification is that it focused entirely on reducing stroke count, and therefore created some very similar-looking character pairs, such as she4 设 (design) and mei2 没 (as in meiyou), or feng1 风 (wind) and feng4 凤 (phoenix). So there is less differentiation of simp. characters and this can make them harder to read.