I don't know if this'll help or not, but with my 5th graders, I refer to inferencing as being a reading detective. I compare it to hearing just one side of a telephone conversation and "figuring out" the rest of the conversation. Then, I'll read them a picture book and we'll infer things about it--maybe the setting, since most picture books don't spell out a specific time and place but you can usually figure it out by looking at the pictures. This is one of the hardest skills for my gang and I look for every opportunity to work it in throughout the year.
With primary (oh, heck - with my 8th graders who still need support!) I would start with wordless picture books. It's something familiar to them, but they need inferencing to "get it". Have them try to explain how they know a certain thing is happening. I've used just one interesting photo for this as well. It really helps them to understand how inferencing works before they move on to text.
Voices in the Park, by Anthony Browne (I think) is a FANTASTIC childrens book to use for inferencing. It tells a story from 4 differnt perspectives about a day at the park. All fur characters meet each other, but the story is told differently by each of them. Then the illustrations are really neat. Like it might be a couldy day for one of the characters (inference---they are sad) then the same day, from a differenct character...it may be sunny (inference--they may be happy) There are also many things in the words that help students inference, you can really get to know the characters just by making inferences. It's great!
To introduce the concept I tell them to guess how I am feeling. Then I walk around, stomping my feet with a grouchy look on my face and my arms crossed. Of course they guess that I am mad! We talk about the "clues" that they used to figure that out. Then I do the same but walk around with a big smile on my face and they infer that I am happy and we discuss those "clues". I do this with sad too. We talk about the fact that I didn't use any words, but they could tell how I felt by my actions.
I teach my 2nd graders that it is using the "clues" they read in the text and what you already know in your head to figure out what is going on in the story or predict what is going to happen.
I took your advice and ordered Voices in the Park for an inference lesson I am doing for my observation. I love the book and the various perspectives taken by the characters. Did you use any specific organizer, or how did the students demonstrate that they were able to prove their inferences, or was the book read by you and was there a verbal discussion? I don't know why but everytime I have an observation I get into a state of panic, even though I've been teaching for years. Any advice you can give me will be appreciated. Thanks!