Building a planter box.

I thought I would ask and see if anyone had advice on building a Planter box. This is what I go going on. I want to kill a few birds with one build.

#1 I want to add seating around my deck
#2 I want to add some privacy buy planting some shrubs in a box and making a "plant wall"

I thought If I built a Bench that had a planter box at the rear of it it would work out pretty good. Here is a rough Ideal what I want to build.

I have never built a planter pox and wanted to know what kind of wood should one use and how should it be lined or how does drainage work ect,

I plan on using a shrub called pittosporum (Pittosporum tobira "Variegata")

its a pretty light weight bush and works well when they are trimmed back and thinned out as a plant wall