what lens/lenses have you got?
if you look on my flickr I have been doing a few in the last few weeks.
my tips ( allthough no expert)
use a long lens from a distance if possible to lessen the angle.
dont use a sunny day, use a day with even lighting.
correct the distortion in your editing software
Camera: Canon EOS 450D
Exposure: 0.017 sec (1/60)
Aperture: f/8.0
Focal Length: 63 mm
Exposure: +0.50
ISO Speed: 100
Exposure Bias: -2 EV
Flash: Off