One thing that is very effective is to read a newspaper article in small sections, then stop, look up, and verbally state what you have just read. Do this until you are sure you have accurately repeated the sections of the article, then continue until you have finished the entire thing.
Doing this forces you to pay closer attention to what you are reading. If there are words in the article you do not understand, look them up in a dictionary, write them down, and memorize their meanings. Review this list every so often to make sure you have not forgotten the words and their meanings.
Newspapers are written on 6th grade reading level, so they are the best place to learn to improve your reading comprehension.