hi there
so basically the whole lot then, only kidding.
client details etc, i would suggest a crm program, you can then store all their details, communications,letters, emails etc, so that you have a client history, a lot of the crm systems can retriive data from the ms office suite.
costings, is a great area, i used to have an autmoated excel ss that would after inputting raw data and tick boxes, then construct the price of the quote, but would also then generate the letter, and spec to be sent to the client, i am now going down the route of developing an ipad front end, excel based system, so that i can do a survey on site, and before ive sat back down with the client i have the quote in front of me. i need to do some work on this so that i can be using it later in the year. the plan is then to use that method on every client visit.
you could go down the route of buying the sage software, as they do the accounting and crm systems, which i believe can talk to each other.
dont know if any of that helps.
regards
martin