Māgha Pūjā, traditional celebrating and todays

Not only as a reminder today, on Māgha Pūjā, it is possible of interest to know more about "Buddhist" secound large Pūjā and it would be interesting to get known different traditional customs (of course not that what is found on wiki, which has "real" info) and one or another might share "first hand" information around it, in Sangha spheres. What are the customs, their reasons, their ways of putting them into deeds? May all use the lasting hours for their long time benefit and cleaning!