Finding interesting texts for beginners can be more difficult. You need to reinforce the vocabulary they know rather than give them too many new words, which means it is difficult for them to understand the text. Of course you can use children’s picture books, but if you are teaching teenagers or adults these often won't be appropriate. And even kids' books can use a lot of new words. One option if you have a very low level class is to use the English Short Stories for Complete Beginners. This will help them read but won't give them complicated vocabulary.
Teaching your students to use dictionaries is important at every level. Either a bi-lingual dictionary or a picture dictionary for lower levels, or a single language dictionary for advanced students. Encourage them to look up words they don't know, and not guess them. If a student looks up a word, they are more likely to remember it, and you can be sure they understand the meaning.
In class, reading can become a little boring. You can make your reading lessons livelier by trying some of the following techniques. Most of them can be adapted to suit any level.
Each pair of students has two connected texts. Each reads and then gives their partner a summary of their text.
Instead of you giving the students the comprehension questions, get them to write their own.
Ask questions to see how much the students remember.
Cut the text up in sections. Place them around the class. Students work in small groups to find a complete set and put them in order.
Ask them to find an example of a certain grammar point or a synonym for another word. They raise their hand when they find it.
If you want your students to learn to read English then the most important thing they can do is practice. That isn't something you can force them to do. Make them aware of where they can get appropriate reading material and you will be giving them the best help you can.