Do not miss the other important topics of IT construction: documentation and testing and debugging. Documentation is an ongoing task in all development phases. Testing and debugging has to be done on different levels: modules, programs, subsystems, system.
First and foremost you should have good programmers around in order to be able to create good quality systems.
For testing I have created an Excel © application which provides test data of different data types and with specified statistical features.
If you do not want to lose any number precision when storing your tab as csv file with Excel 2010 or older versions then look here.
One important part of IT quality is data integrity and consistency.
If delivering a software make sure that your customer will receive official notification about delivery date, necessary training and first week/month support. If you have to make 3 or more emergency changes on your software within the first week of production you definitely developed poor quality.
A small documentation example is presented here.
A somewhat exotic but nevertheless important aspect of IT quality is a solution approach which is
a) efficient (in terms of runtime, storage usage, etc.) and
b) manageable (in terms of complexity and maintainability).
For Excel © array formulas - sometimes also called matrix formulas - I postulate my w-rule of IT quality here.