What tricks help readers with tracking?

Ms. Dorothy,
______ is struggling with his reading, especially when he is reading out loud.  He has a hard time keeping track of the line he is reading when he goes down to the next line.  I've tried using a book mark or a piece of paper under the line, but it almost seems to slow him down even more.  Are there other tricks that can help him?
- 3rd grade Mom

Reading is much less about translating a word at a time, and much more about making sense of phrases and sentences and ideas in chunks.  It may be that he is self-conscious about the accuracy of his word call when reading aloud, and questioning himself is what slows him down.

It is important that he be able to see the words in the lines following what he is reading because the information we gather by scanning ahead is more helpful for fluent reading than anything else. 

If you are going to cover lines to help him track, try covering the line above what he is reading rather than below.

Some people find reading black letters on white pages is difficult because there is too much dramatic contrast.  Try experimenting with pieces of colored cellophane to find a color that feels comfortable to his eyes.

My final suggestion would be to be sure he has a thorough eye exam to rule out any physical problems that may be interfering with his reading.