Headlamp aim

Headlamp aim is easiest reproduced, so if you are removing a headlamp work out where the beam is aimed on a wall first, then you can put it back there when you have finished.

The basic rule for aim adjustment is that the high beam should point directly ahead of the bulb/lenses/reflectors. Dipped beam is a little more complex, it is explained in the following:

http://www.motuk.co.uk/manual_160.htm

http://www.dvtani.gov.uk/uploads/customerservices/Headlampleaflet.pdf

http://www.carinsurance.com/Articles/content169.aspx

These are an excellent articles, however they describe US laws and regulations, which may or may not relate to UK policies:

http://faqlight.carpassion.info/hl-aiming.htm

http://www.danielsternlighting.com/images/Aim.pdf