I fell into the trap of looking at other peoples aerials on-site recently, and was really struggling to get a decent signal.
Then I looked on the website and found the polarisation was vertical and not horizontal like everyone around us had. Changed ours to vertical and we had a perfect signal.
Don't assume that people around you know what they are doing !
The website also gives you the bearing, so we now keep a compass in the van and setup takes a few mins.
If you have a smart phone there is an app that will give you a map of the nearest transmission masts and the strength, bearing and polarisation. No need for compass as it displays a pointer on the phone. UK aerial alignment is the one I use but there are others.
------------- 'A sure cure for sea-sickness is to sit under a tree'