My target audience are users that are not familiar so much with computers so i try to simplify the UI elements in use as much as possible.
For instance I try to avoid drop down menus and use big radio buttons instead (when possible).
Now I have to provide a multiple select option list. I could use check boxes but there are just too many properties. It seems that there is no simple component to allow such an action.
Here are several options:
Regular Multiple select
Custom made scrollable box with chekboxes
Multiple select drop-down with checkboxes
None of them seem simple enough for me. The 1st one is the worst I believe as it asks the user to press ctrl to multi-select. Are there any other options you have in mind? Is there any research on the subject ?