Know your boundary lines and foresee any potential consequences should any part of these trees cross your neighbor's property line both above and below ground. Example, whereas your neighbor had a sunny window and a bright room, the plantings might turn it to exactly the opposite. Also, leaf dropping trashing their property. Or shallow roots affecting drainage and hardening their ground to make planting difficult for them. In any case have a little talk with them to see which way the wind blows. I know it's your property and you can do what you want(to a certain point), but, showing consideration before you start planting helps make good neighbors. As far as what to plant I would suggest you give members an idea of the length of the property line. A photo would help in that the less assumptions the members have to make the better the answers will be. What you propose to plant is rather large and spacing will have to be taken into account as your plantings mature over the years, and yes, it may take YEARS to achieve the privacy you desire with this method of obtaining it.

Would help enormously to know whether the area is in sun, half sun, or very shady - also what part of the country you're in to gauge temperatures. Did you also want these privacy plants to be evergreen, or can one or two of them drop their leaves because privacy isn't such an issue in winter?

It isn't always a good idea to plant actual trees on a boundary line as half the top growth will be on your neighbour's side and they are legally entitled to cut off any overhang. Could you tell us please how the boundary is marked now, eg post and wire, fence etc?

But without any further info I will say whatever you do,don't plant leylandii.

Or privet! (As in don't plant privet)

A 6ft fence should provide more than enough privacy unless their land is higher than yours or they are related to Peter Crouch.

Beware!! Most things that grow to 8-10 feet don't stop at 8-10 feet and if they are evergreen 2 or more of them will then move into the high hedges category.