Appeal to the students' natural interests by incorporating such things as well-known individuals, sports, music or current fashions into the math problems. Every math teacher has been asked, with a groan, "When are we ever going to use this?" Instead of telling students they just have to learn it, they might be in an occupation that relies on algebra or it helps them learn to think, relate the pre-algebra concepts to real life.
Use visuals and manipulatives whenever possible. Graphs, pie charts and Base 10 blocks lend themselves to learning algebraic concepts. The more of the senses involved in the learning experience, the easier the learning becomes.
Set up learning centers with a 15- to 20-minute daily challenge to solve, allowing students to review the day's material at their own pace. The students have an opportunity to get up and move around, often paying better attention when they return to their desks.
Divide the class into small groups to work on problems, or set up one-on-one tutoring for students needing extra help. Students can sometimes teach their peers more effectively than the instructor.
Explain your reasoning as you demonstrate pre-algebraic concepts, and require the same of the students. If they can't explain what they're doing, they don't know the material. Listening to repeated explanations of the process will help cement the process in the students' minds. Practice, practice, practice!
Teach with enthusiasm and a positive attitude. It will be infectious. Nothing encourages boredom like listening to a bored instructor. Don't berate a student or allow others to make fun of him. Take time to explain, and don't be afraid to use humor.