Id recommend always get a professional fitter who is recommended by Amtico & Karndean, you can ring them and ask them for a fitter in your area.
If you insist on DIY - then make sure the floor is level - either ply the floorboards using a 6mm marine ply or on concrete floors use a self levelling compound and leave for 24 hours ( you can usually walk lightly on it after 4 hours).
Use the recommended adhesive - Amtico & Karndean have there own adhesive and its best to use the particular one they recommend - for areas that get a lot of sunlight or have underfloor heating they recommend a High Temperature Adhesive and for wet areas they recommend a 2 part adhesive (which is very difficult to work with and would only attempt this by yourself if your a very very experienced DIYer!)
Start in the centre (like tiling a wall) to ensure outside cuts are even spread a little adhesive at a time and wait for it to go tacky then your ready to start.
For more information visit Amtico & Karndean websites and search on installation for more help
Nicky - T J Hill Flooring
Hope its been helpful for general help and advice contact me Nicky 01543 277174 or mobile 07846602174 or out of hours at home (I really dont mind) on 01543 276871.