Don't preach - pray with and for people, not at them . Avoid repetition, platitudes, complicated language, confused pauses. Similarly, clear off fairly quickly too so that the Confession runs nicely from the prayers. Avoid paper shuffling. Microphone is good, you can use tone and volume to great effect - be audible, clear but not intrusive.
Some people systematically ignore what the intercessor says - they switch off deliberately.
Lead them - Pause before 'Lord in your mercy' etc. When speaking to God - love Him. When leading others - love them. Never be anything other than human in the presence of God. Prayer is not a technique - it is a dialogue of love.