When you want to share data with others, the first thing you need to decide is under what terms. Do you want others be able just look at the data, change the format (Excel to CSV, for example)? Do you want this person to be allowed to share the data within his research group, or perhaps collaborators?
Very often this is arranged informally, in good faith, or by some consortium, confidentiality, or non-disclosure agreements. However, these approaches do not scale very well. When this matters, then data licenses are an alternative approach (not necessarily better!).
Madeleine Gray has written on her EUDat blog some words about the EUDAT License Wizard. This wizards talks you through the things you like to agree on, and in the end suggests a possible data license. It seems pretty well done, and the first few questions focus on an important aspect: do you even have the rights to change the license (i.e. you are the copyright owner).
Mind you, there are huge differences between countries around data copyright.