I've had similar experiences. So far I've tried the normal method of reading through the entire passage then answering the questions with going back to clarify information I can't remember accurately. I've also tried Vicviper's method of doing the opposite, reading all the questions first, then looking for answers in the passage. The first/normal method worked slightly better for me.
A different method I recently tried was simply to read 1-2 paragraphs, then skim the questions quickly to see if any could be answered with what I read, then repeating for the next 1-2 paragraphs. I found this worked best for me, as I could remember very clearly what I read in just 1-2 paragraphs, it also removed the need to re-read anything, since I could essentially eliminate what I had already read, this I think is a huge time saver, as having to go back over the entire passage looking for answers can take forever and be frustrating.