planning is very important. think about it, and think some more.... little tips like think about being able to open your dishwasher and load clean dishes straight into a nearby open cupboard for example...without careful planning, you can miss little things that make your kitchen really work for you.....
consider what you have to store, and where you will store them in a kitchen cupboard plan. this will help with knowing whether you need more drawers/cupboard/shelves etc..
if you are doing building work and are having problems visualising what space you will have, take your measurments to showrooms and a tape measure and look at what unit layouts are pleasing to the eye, providing how much space etc...
negotiate. don't be afraid of fluttering your eyelashes to get discounts!
i got my ideal kitchen way down to within my budget by being a bit charming....
source things separately...we got our units and worktops from howdens. our appliences were from a local warehouse store, saving THOUSANDS because they were last years models...all brand new with guarantees though.
we fitted it ourselves. took bloody ages, and was hard work, but end result is fab... we bought in a guy to butt and scribe the worktops, plumber friend to connect the cooker up etc... it meant that we could spend money on our kitchen rather than on fitting.
fwiw, our total budget was 5K, that was for kitchen, worktops, all appliances, flooring, curtains etc, and we have a largeish kitchen with solid wood doors, and we came in bang on.
hth. its a really exciting thing to do, and the end result is fab!!!