To get valid evidence about aging, studies should be as inclusive as possible by targeting also the oldest old section and those with disabilities. Participant involvement is paramount in studies that concern older people’s well-being and services promoting well-being. To battle traditional and even ageist views about older people, it is recommended that measures assessing both positive and negative dimensions of well-being and functioning are included to create a more balanced description of the situation. Considering participant burden is a key factor in planning a successful study. It is important not to overestimate or underestimate the participants’ ability to contribute. Finally, before setting up new studies, familiarizing with studies providing open-access data may be worthwhile. There may already be relevant data available which will speed up answering research question markedly.