When buying new appliances, buy a quieter model - not all models have a noise rating, but look out for the "Quiet Mark".
Where possible, position them to cause the least disturbance to your neighbour.
For washing machines, if possible, place on an even floor; do not overload and run the machine at a time when it will least disturb neighbours - remember the final spin is the noisiest bit.
Do the vacuuming at a reasonable time - especially if you live in a flat or terrace, avoid early morning or late night cleaning sprees.
In the kitchen, avoid banging pans and cupboard doors and don't use blenders/grinders on surfaces attached to party walls.