Plan ahead to organise the information so that it's structured, so it's easier for student, all students, to follow. Provide regular breaks, and if you have a three hour lecture without any breaks, I don't think any student can concentrate for that long. Particularly if you have, for example, a student with a hearing impairment or for some reason is having to concentrate that much harder, to be able to just stop for a short time and close your eyes and know that you're not going to miss anything, is really important.