You can do this usually without too much trouble. Step 1 is to get your router as high as feasible and also as near the middle of the hoped for coverage area. If you want to extend this to your neighbour, then bias towards their property.
Step two is to have a look at the router manufacturers website and other specialist broadband suppliers (PM for details) for high gain aerials and range extenders.
That should sort you out.
Conan