British Columbia: Pruning lilac trees

I have 3 lilac trees that are getting very leggy and the neighbours are getting all the benefit of the blossoms. I would like to prune them so that the blossoms start lower down. Anyone out there know how to do it and when to do it? The blossoms are just starting to fade now. thanks
MK

 

Lilacs are most floriferous if never pruned at all. Pruning may result in up to 5-7 years with no flowers at all, while the plant is rebuilding a framework of new branches. So go easy on any pruning!

 

Cut all or part of the stems down to 18" next winter. And if there is something overtopping them, so that only the branches hanging over the neighbor's side are getting full light, try to prune that back so that the rest of the planting gets a more favorable exposure.