How to collect user data and keep it up to date

We have already discussed the opt in and the need to keep our forms short to reduce friction in the registration process, but this need competes with the need to collect as much user information as we can. To reconcile these objectives, we can apply a progressive data collection.
In this image from Marketo we can see how the length of a form affects conversion.

The Progressive Profiling allows us to take advantage of the benefits of a short registration form and, once registration has been achieved, to expand the information we have available. In order to gather this information, we can use a centre of preference where the user can fill in and update their information. Often, to take advantage of the user's interaction, the preference centre appears just after the registration, as we see in this case of KIABI:

Giving access the user to the preference centre, e.g. with a permanent link in the emails, is often not enough. Ideally, the existence of the preference centre should be communicated through ad hoc mailings and make the user aware of the benefits of sharing their information with us (messages that are tailored to their interests, personalised offers, etc.). We must use creativity and take advantage of this to strengthen the relationship with the user, Let us avoid being aloof, we must make the user place their trust in us. It is effective to offer incentives such as discounts, participation in raffles and exclusive offers...
We can also use forms for concrete actions. It is advisable that these forms are very visual and that we formulate the questions so that they work as a hook. For example, let's imagine that a fashion retailer wants to know what kind of products a customer is interested in during a specific period such as Christmas. With this information, they can adjust the content of the emails they send during this period. Normally in the preference centre you would find this explicit option, a section to select interests, but if you create an action to collect this data in a more indirect way, it could be something like this:

Let us not forget that it is not only a matter of collecting this information, but also of keeping it updated, so it is advisable to carry out campaigns with this objective periodically. Obtaining as much information from our users as possible and keeping it updated ensures more relevant and, therefore, effective communications.