Yes, if you remove the faded blooms from your lilac shrub after the plant flowers you will allow the plant more energy to go into new growth rather than seed production. You can also renovate a lazy lilac by cutting back the oldest branches (the ones most thick) but cutting to within two feet from the ground. This allows the younger more vigorous shoots to take over. You can remove one third of the thickest trunks each year. Shorten any long thin branches by one third as well. Be sure to fertilize with a slow release plant food like Osmocote this spring and mulch the soil around the roots before the heat of summer arrives. Lilacs like full sun and an exposed or windy location to bloom at their best. If your lilacs dry out in the summer they may survive but have less blooms the following spring. The mulch  will help to seal in moisture. If you do water this summer do not get the foliage wet as many lilacs are susceptible to leaf blights. Keep growing, Marianne Binetti