current salary - give 'em the facts including whatever extras you get. if you get such things like non-contrib pension payments, guaranteed bonuses the list them (with numbers or % if pension) as these are technically income as you will be taxed on them. if you get performance related bonuses, put an OTE figure down
future salary - to be discussed at interview
sure, when you move jobs most people are looking for more money and usually some form of advancement, but people can make mistakes by pushing the boat out too far in % increase they are looking for. you have to be realistic.
as a recruiter, I handle these things all the time - you need to be realistic or potential employers won't be interested