You might be considering including a privacy hedge into your landscape either for the obvious, privacy, or just to put a nice even border around your yard or garden area. 

The best plants that would require the least amount of maintenance would be Privets, Junipers, Lilacs and Buckthorns to name a few.  There are varieties within these types of plants as well so you have various choices.  You'll want to consider how high you want your hedge, how full you want it as well as do you want it to be evergreen or deciduous?  You might also want to make sure that if it's deciduous that the branches have a look you will enjoy during the winter when there are no leaves.  Also, do you want it to flower or fruit and take into consideration that the flowering and fruiting may cause some extra cleanup.

Privets are generally inexpensive, grow fast and may only need pruning twice a year.  Buckthorns can be a little more costly but they basically need little to no pruning.  Lilacs will flower and add a wonderful fragrance but they do lose some of their petals.  Some will also fruit which can attract birds and wildlife. 

Whatever you decide to do, there is definitely a plant that will fit your needs and desires for a privet hedge.