At a recent training day with Sandra Millar in Leicester, I have used an idea she shared that has been really well received, (see p.16 of Sandra’s book Worship Together SPCK 2012)
A small basket containing artificial rose petals is placed next to the font and all in the congregation are encouraged to place a petal in the water if they want to remember their own baptism at this time, (I do know that Sandra impregnates her petals with scent each time).
At one of my churches, where the font is at the back by the door, I encourage them to do it as they leave. At another, where a small font is placed at the front, I make it a feature of the service and have quiet music playing.
The petals I use were sourced from ebay and are re-usable after drying out, the baskets I use came from a Pound Shop. [NB The petals pictured are not those used by Rob]
At one service in which I used this idea, over 80 people out of a congregation of 100 took part.