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.
Place washing machines on an even floor; do not overload them and run them a time when it will least disturb neighbours - remember the final spin is the noisiest bit.
Do the vacuuming at a reasonable time and avoid early morning or late night cleaning sprees.
In the kitchen, avoid banging pans and cupboard doors and don not use blenders/grinders on surfaces attached to party walls.