The best leaflet is the one you hand to the customer personally, canvassing them at the same time. I started 3 years ago; I printed 3000 leaflets; I canvassed for 3 months and have never knocked a door / delivered a leafet since. Total advertising spend aside from leaflets £10 + website (done in return for a clean and I now pay a twice yearly hosting charge of £70-ish). I've a great balance of custies, with a whole load more on the way now spring is round the corner (i've tended to grow the customer base by around 15% year on year just by word of mouth recommendation/website/seeing the van.
I've never dropped leaflets, nor would I. I think to myself what I do with junk mail - I bin it.