There are lots of learned articles about this, but here�s my twopen �orth briefly:
Some pupils may be weak in this skill due to lack of practice; lack of needing to perform the skill. Students tend to google answers for their questions, rather than trawling through lots of material to get the key points they need to know. Teachers can develop the skill by:
Highlighting: Give the students a lengthy passage, with just 2 or 3 questions. Help them to highlight key words in the question, and then to find the same key words in the passage. Then, read the sentences around the key words and provide the answer.
Envoy: Students are working in groups. They all have the same passage, but they have different questions - maybe 2 questions per group. Set a time, then after that time, they move round tables, collecting the other answers (or one �envoy � goes from group to group).
Speed reading: Give them a passage and a question and 1 or 2 minutes (or whatever you think) to find the answer.
Tally: Give out the passage and give them an allotted time limit to count how many times a key word appears.
Any activity really, that gets them to seek out key pieces of info from a text.
Just a few ideas!