How do you help students who are struggling with reading comprehension?

Many pre-reading and during-reading prompts and exercises are useful to improve a student's reading comprehension. I also want to identify where the trouble is stemming from--is the vocabulary too difficult, does the student have trouble with sight words, is there a phonics issue, etc. That way I can address the issue in a targeted way.

How would you help a student get excited/engaged with a subject that they are struggling in?

I want to provide opportunities for the student to succeed early on so that they can build on their wins. I also try to relate the subject matter to the student's interests.

What techniques would you use to be sure that a student understands the material?

I explain concepts with simpler examples before applying them to more sophisticated contexts. I also do spot comprehension checks throughout lessons to ensure that the student is following.