Start where the students are. There is no point in lecturing about topics or concepts low-level students can't comprehend. In addition to delivering the lecture at their level, be sure to speak clearly and to enunciate your words properly. Speak slowly and don't rush.
Deliver your lectures in short sharp units. Rather than the standard 50 minute lecture, break your time with low-level students into a 10 minute lecture, followed by a five minutes discussion. Low-level learners often have short attention spans, so use a variety of activities in your lectures so the students stay focused.
Have students take notes when you lecture. Show them how to jot down points they need to remember and how to review the material later to refresh their memories. Check their notebooks from time to time to see how well they are following your instructions.
Write notes on the board. In addition to having the students take their own notes, supplement your lecture by writing important point on the board. Be sure the students copy them into their notebooks.
Ask frequent questions to make sure the students are following you. Listen to the students' verbal responses and watch their body language as it will give you an indication if they are understanding your lecture.
Invite the low-level students to immediately ask questions when they don't understand a point. Whereas some lecturers ask students to hold their questions until the end, with low-level students it is better to encourage them to ask the question when they think of it. Chances are they will forget by the end of the lecture, even if it is only 15 minutes.